contextlib2 — Updated utilities for context management¶
This module provides backports of features in the latest version of the
standard library’s contextlib module to earlier Python versions. It
also serves as a real world proving ground for potential future enhancements
to that module.
Like contextlib, this module provides utilities for common tasks
involving the with statement.
This module is primarily a backport of the Python 3.5 version of
contextlib to earlier releases. However, it is also a proving ground
for new features not yet part of the standard library.
There are currently no such features in the module.
Refer to the contextlib documentation for details of which
versions of Python 3 introduce the various APIs provided in this module.
This function is a decorator that can be used to define a factory
function for with statement context managers, without needing to
create a class or separate __enter__() and __exit__() methods.
A simple example (this is not recommended as a real way of generating HTML!):
The function being decorated must return a generator-iterator when
called. This iterator must yield exactly one value, which will be bound to
the targets in the with statement’s as clause, if any.
At the point where the generator yields, the block nested in the with
statement is executed. The generator is then resumed after the block is exited.
If an unhandled exception occurs in the block, it is reraised inside the
generator at the point where the yield occurred. Thus, you can use a
try...except...finally statement to trap
the error (if any), or ensure that some cleanup takes place. If an exception is
trapped merely in order to log it or to perform some action (rather than to
suppress it entirely), the generator must reraise that exception. Otherwise the
generator context manager will indicate to the with statement that
the exception has been handled, and execution will resume with the statement
immediately following the with statement.
contextmanager() uses ContextDecorator so the context managers
it creates can be used as decorators as well as in with statements.
When used as a decorator, a new generator instance is implicitly created on
each function call (this allows the otherwise “one-shot” context managers
created by contextmanager() to meet the requirement that context
managers support multiple invocations in order to be used as decorators).
Return a context manager that suppresses any of the specified exceptions
if they occur in the body of a with statement and then resumes execution
with the first statement following the end of the with statement.
As with any other mechanism that completely suppresses exceptions, this
context manager should be used only to cover very specific errors where
silently continuing with program execution is known to be the right
thing to do.
Context manager for temporarily redirecting sys.stdout to
another file or file-like object.
This tool adds flexibility to existing functions or classes whose output
is hardwired to stdout.
For example, the output of help() normally is sent to sys.stdout.
You can capture that output in a string by redirecting the output to a
io.StringIO object:
Note that the global side effect on sys.stdout means that this
context manager is not suitable for use in library code and most threaded
applications. It also has no effect on the output of subprocesses.
However, it is still a useful approach for many utility scripts.
A base class that enables a context manager to also be used as a decorator.
Context managers inheriting from ContextDecorator have to implement
__enter__ and __exit__ as normal. __exit__ retains its optional
exception handling even when used as a decorator.
ContextDecorator is used by contextmanager(), so you get this
functionality automatically.
Example of ContextDecorator:
from contextlib import ContextDecorator
class mycontext(ContextDecorator):
def __enter__(self):
print('Starting')
return self
def __exit__(self, *exc):
print('Finishing')
return False
>>> @mycontext()
... def function():
... print('The bit in the middle')
...
>>> function()
Starting
The bit in the middle
Finishing
>>> with mycontext():
... print('The bit in the middle')
...
Starting
The bit in the middle
Finishing
This change is just syntactic sugar for any construct of the following form:
def f():
with cm():
# Do stuff
ContextDecorator lets you instead write:
@cm()
def f():
# Do stuff
It makes it clear that the cm applies to the whole function, rather than
just a piece of it (and saving an indentation level is nice, too).
Existing context managers that already have a base class can be extended by
using ContextDecorator as a mixin class:
As the decorated function must be able to be called multiple times, the
underlying context manager must support use in multiple with
statements. If this is not the case, then the original construct with the
explicit with statement inside the function should be used.
A context manager that is designed to make it easy to programmatically
combine other context managers and cleanup functions, especially those
that are optional or otherwise driven by input data.
For example, a set of files may easily be handled in a single with
statement as follows:
withExitStack()asstack:files=[stack.enter_context(open(fname))forfnameinfilenames]# All opened files will automatically be closed at the end of# the with statement, even if attempts to open files later# in the list raise an exception
Each instance maintains a stack of registered callbacks that are called in
reverse order when the instance is closed (either explicitly or implicitly
at the end of a with statement). Note that callbacks are not
invoked implicitly when the context stack instance is garbage collected.
This stack model is used so that context managers that acquire their
resources in their __init__ method (such as file objects) can be
handled correctly.
Since registered callbacks are invoked in the reverse order of
registration, this ends up behaving as if multiple nested with
statements had been used with the registered set of callbacks. This even
extends to exception handling - if an inner callback suppresses or replaces
an exception, then outer callbacks will be passed arguments based on that
updated state.
This is a relatively low level API that takes care of the details of
correctly unwinding the stack of exit callbacks. It provides a suitable
foundation for higher level context managers that manipulate the exit
stack in application specific ways.
New in version 0.4: Part of the standard library in Python 3.3 and later
Enters a new context manager and adds its __exit__() method to
the callback stack. The return value is the result of the context
manager’s own __enter__() method.
These context managers may suppress exceptions just as they normally
would if used directly as part of a with statement.
Adds a context manager’s __exit__() method to the callback stack.
As __enter__ is not invoked, this method can be used to cover
part of an __enter__() implementation with a context manager’s own
__exit__() method.
If passed an object that is not a context manager, this method assumes
it is a callback with the same signature as a context manager’s
__exit__() method and adds it directly to the callback stack.
By returning true values, these callbacks can suppress exceptions the
same way context manager __exit__() methods can.
The passed in object is returned from the function, allowing this
method to be used as a function decorator.
Transfers the callback stack to a fresh ExitStack instance
and returns it. No callbacks are invoked by this operation - instead,
they will now be invoked when the new stack is closed (either
explicitly or implicitly at the end of a with statement).
For example, a group of files can be opened as an “all or nothing”
operation as follows:
withExitStack()asstack:files=[stack.enter_context(open(fname))forfnameinfilenames]# Hold onto the close method, but don't call it yet.close_files=stack.pop_all().close# If opening any file fails, all previously opened files will be# closed automatically. If all files are opened successfully,# they will remain open even after the with statement ends.# close_files() can then be invoked explicitly to close them all.
Immediately unwinds the callback stack, invoking callbacks in the
reverse order of registration. For any context managers and exit
callbacks registered, the arguments passed in will indicate that no
exception occurred.
This section describes some examples and recipes for making effective use of
the tools provided by contextlib2. Some of them may also work with
contextlib in sufficiently recent versions of Python. When this is the
case, it is noted at the end of the example.
As noted in the documentation of ExitStack.push(), this
method can be useful in cleaning up an already allocated resource if later
steps in the __enter__() implementation fail.
Here’s an example of doing this for a context manager that accepts resource
acquisition and release functions, along with an optional validation function,
and maps them to the context management protocol:
fromcontextlib2importExitStackclassResourceManager(object):def__init__(self,acquire_resource,release_resource,check_resource_ok=None):self.acquire_resource=acquire_resourceself.release_resource=release_resourceself.check_resource_ok=check_resource_okdef__enter__(self):resource=self.acquire_resource()ifself.check_resource_okisnotNone:withExitStack()asstack:stack.push(self)ifnotself.check_resource_ok(resource):msg="Failed validation for {!r}"raiseRuntimeError(msg.format(resource))# The validation check passed and didn't raise an exception# Accordingly, we want to keep the resource, and pass it# back to our callerstack.pop_all()returnresourcedef__exit__(self,*exc_details):# We don't need to duplicate any of our resource release logicself.release_resource()
This example will also work with contextlib in Python 3.3 or later.
Replacing any use of try-finally and flag variables¶
A pattern you will sometimes see is a try-finally statement with a flag
variable to indicate whether or not the body of the finally clause should
be executed. In its simplest form (that can’t already be handled just by
using an except clause instead), it looks something like this:
As with any try statement based code, this can cause problems for
development and review, because the setup code and the cleanup code can end
up being separated by arbitrarily long sections of code.
ExitStack makes it possible to instead register a callback for
execution at the end of a with statement, and then later decide to skip
executing that callback:
If the resource cleanup isn’t already neatly bundled into a standalone
function, then it is still possible to use the decorator form of
ExitStack.callback() to declare the resource cleanup in
advance:
Due to the way the decorator protocol works, a callback function
declared this way cannot take any parameters. Instead, any resources to
be released must be accessed as closure variables.
This example will also work with contextlib in Python 3.3 or later.
ContextDecorator makes it possible to use a context manager in
both an ordinary with statement and also as a function decorator. The
ContextDecorator.refresh_cm() method even makes it possible to use
otherwise single use context managers (such as those created by
contextmanager()) that way.
For example, it is sometimes useful to wrap functions or groups of statements
with a logger that can track the time of entry and time of exit. Rather than
writing both a function decorator and a context manager for the task,
contextmanager() provides both capabilities in a single
definition:
withtrack_entry_and_exit('widget loader'):print('Some time consuming activity goes here')load_widget()
And also as a function decorator:
@track_entry_and_exit('widget loader')defactivity():print('Some time consuming activity goes here')load_widget()
Note that there is one additional limitation when using context managers
as function decorators: there’s no way to access the return value of
__enter__(). If that value is needed, then it is still necessary to use
an explicit with statement.
This example will also work with contextlib in Python 3.2.1 or later.
Single use, reusable and reentrant context managers¶
Most context managers are written in a way that means they can only be
used effectively in a with statement once. These single use
context managers must be created afresh each time they’re used -
attempting to use them a second time will trigger an exception or
otherwise not work correctly.
This common limitation means that it is generally advisable to create
context managers directly in the header of the with statement
where they are used (as shown in all of the usage examples above).
Files are an example of effectively single use context managers, since
the first with statement will close the file, preventing any
further IO operations using that file object.
Context managers created using contextmanager() are also single use
context managers, and will complain about the underlying generator failing
to yield if an attempt is made to use them a second time:
More sophisticated context managers may be “reentrant”. These context
managers can not only be used in multiple with statements,
but may also be used inside a with statement that is already
using the same context manager.
threading.RLock is an example of a reentrant context manager, as is
suppress(). Here’s a toy example of reentrant use (real world
examples of reentrancy are more likely to occur with objects like recursive
locks and are likely to be far more complicated than this example):
>>> fromcontextlibimportsuppress>>> ignore_raised_exception=suppress(ZeroDivisionError)>>> withignore_raised_exception:... withignore_raised_exception:... 1/0... print("This line runs")... 1/0... print("This is skipped")...This line runs>>> # The second exception is also suppressed
Distinct from both single use and reentrant context managers are “reusable”
context managers (or, to be completely explicit, “reusable, but not
reentrant” context managers, since reentrant context managers are also
reusable). These context managers support being used multiple times, but
will fail (or otherwise not work correctly) if the specific context manager
instance has already been used in a containing with statement.
Updated to include all features from the Python 3.4 and 3.5 releases of
contextlib (also includes some ExitStack enhancements made following
the integration into the standard library for Python 3.3)
The legacy ContextStack and ContextDecorator.refresh_cm APIs are
no longer documented and emit DeprecationWarning when used
Python 2.6, 3.2 and 3.3 have been dropped from compatibility testing
Issue #8: Replace ContextStack with ExitStack (old ContextStack API
retained for backwards compatibility)
Fall back to unittest2 if unittest is missing required functionality
Issue #7: Add MANIFEST.in so PyPI package contains all relevant files
Issue #5: ContextStack.register no longer pointlessly returns the wrapped
function
Issue #2: Add examples and recipes section to docs
Issue #3: ContextStack.register_exit() now accepts objects with __exit__
attributes in addition to accepting exit callbacks directly
Issue #1: Add ContextStack.preserve() to move all registered callbacks to
a new ContextStack object
Wrapped callbacks now expose __wrapped__ (for direct callbacks) or __self__
(for context manager methods) attributes to aid in introspection
Moved version number to a VERSION.txt file (read by both docs and setup.py)
Added NEWS.rst (and incorporated into documentation)
Renamed CleanupManager to ContextStack (hopefully before anyone started
using the module for anything, since I didn’t alias the old name at all)
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PK y-,H` ` 2 contextlib2-dev-stable/_static/underscore-1.3.1.js// Underscore.js 1.3.1
// (c) 2009-2012 Jeremy Ashkenas, DocumentCloud Inc.
// Underscore is freely distributable under the MIT license.
// Portions of Underscore are inspired or borrowed from Prototype,
// Oliver Steele's Functional, and John Resig's Micro-Templating.
// For all details and documentation:
// http://documentcloud.github.com/underscore
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value : value,
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}).sort(function(left, right) {
var a = left.criteria, b = right.criteria;
return a < b ? -1 : a > b ? 1 : 0;
}), 'value');
};
// Groups the object's values by a criterion. Pass either a string attribute
// to group by, or a function that returns the criterion.
_.groupBy = function(obj, val) {
var result = {};
var iterator = _.isFunction(val) ? val : function(obj) { return obj[val]; };
each(obj, function(value, index) {
var key = iterator(value, index);
(result[key] || (result[key] = [])).push(value);
});
return result;
};
// Use a comparator function to figure out at what index an object should
// be inserted so as to maintain order. Uses binary search.
_.sortedIndex = function(array, obj, iterator) {
iterator || (iterator = _.identity);
var low = 0, high = array.length;
while (low < high) {
var mid = (low + high) >> 1;
iterator(array[mid]) < iterator(obj) ? low = mid + 1 : high = mid;
}
return low;
};
// Safely convert anything iterable into a real, live array.
_.toArray = function(iterable) {
if (!iterable) return [];
if (iterable.toArray) return iterable.toArray();
if (_.isArray(iterable)) return slice.call(iterable);
if (_.isArguments(iterable)) return slice.call(iterable);
return _.values(iterable);
};
// Return the number of elements in an object.
_.size = function(obj) {
return _.toArray(obj).length;
};
// Array Functions
// ---------------
// Get the first element of an array. Passing **n** will return the first N
// values in the array. Aliased as `head`. The **guard** check allows it to work
// with `_.map`.
_.first = _.head = function(array, n, guard) {
return (n != null) && !guard ? slice.call(array, 0, n) : array[0];
};
// Returns everything but the last entry of the array. Especcialy useful on
// the arguments object. Passing **n** will return all the values in
// the array, excluding the last N. The **guard** check allows it to work with
// `_.map`.
_.initial = function(array, n, guard) {
return slice.call(array, 0, array.length - ((n == null) || guard ? 1 : n));
};
// Get the last element of an array. Passing **n** will return the last N
// values in the array. The **guard** check allows it to work with `_.map`.
_.last = function(array, n, guard) {
if ((n != null) && !guard) {
return slice.call(array, Math.max(array.length - n, 0));
} else {
return array[array.length - 1];
}
};
// Returns everything but the first entry of the array. Aliased as `tail`.
// Especially useful on the arguments object. Passing an **index** will return
// the rest of the values in the array from that index onward. The **guard**
// check allows it to work with `_.map`.
_.rest = _.tail = function(array, index, guard) {
return slice.call(array, (index == null) || guard ? 1 : index);
};
// Trim out all falsy values from an array.
_.compact = function(array) {
return _.filter(array, function(value){ return !!value; });
};
// Return a completely flattened version of an array.
_.flatten = function(array, shallow) {
return _.reduce(array, function(memo, value) {
if (_.isArray(value)) return memo.concat(shallow ? value : _.flatten(value));
memo[memo.length] = value;
return memo;
}, []);
};
// Return a version of the array that does not contain the specified value(s).
_.without = function(array) {
return _.difference(array, slice.call(arguments, 1));
};
// Produce a duplicate-free version of the array. If the array has already
// been sorted, you have the option of using a faster algorithm.
// Aliased as `unique`.
_.uniq = _.unique = function(array, isSorted, iterator) {
var initial = iterator ? _.map(array, iterator) : array;
var result = [];
_.reduce(initial, function(memo, el, i) {
if (0 == i || (isSorted === true ? _.last(memo) != el : !_.include(memo, el))) {
memo[memo.length] = el;
result[result.length] = array[i];
}
return memo;
}, []);
return result;
};
// Produce an array that contains the union: each distinct element from all of
// the passed-in arrays.
_.union = function() {
return _.uniq(_.flatten(arguments, true));
};
// Produce an array that contains every item shared between all the
// passed-in arrays. (Aliased as "intersect" for back-compat.)
_.intersection = _.intersect = function(array) {
var rest = slice.call(arguments, 1);
return _.filter(_.uniq(array), function(item) {
return _.every(rest, function(other) {
return _.indexOf(other, item) >= 0;
});
});
};
// Take the difference between one array and a number of other arrays.
// Only the elements present in just the first array will remain.
_.difference = function(array) {
var rest = _.flatten(slice.call(arguments, 1));
return _.filter(array, function(value){ return !_.include(rest, value); });
};
// Zip together multiple lists into a single array -- elements that share
// an index go together.
_.zip = function() {
var args = slice.call(arguments);
var length = _.max(_.pluck(args, 'length'));
var results = new Array(length);
for (var i = 0; i < length; i++) results[i] = _.pluck(args, "" + i);
return results;
};
// If the browser doesn't supply us with indexOf (I'm looking at you, **MSIE**),
// we need this function. Return the position of the first occurrence of an
// item in an array, or -1 if the item is not included in the array.
// Delegates to **ECMAScript 5**'s native `indexOf` if available.
// If the array is large and already in sort order, pass `true`
// for **isSorted** to use binary search.
_.indexOf = function(array, item, isSorted) {
if (array == null) return -1;
var i, l;
if (isSorted) {
i = _.sortedIndex(array, item);
return array[i] === item ? i : -1;
}
if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item);
for (i = 0, l = array.length; i < l; i++) if (i in array && array[i] === item) return i;
return -1;
};
// Delegates to **ECMAScript 5**'s native `lastIndexOf` if available.
_.lastIndexOf = function(array, item) {
if (array == null) return -1;
if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) return array.lastIndexOf(item);
var i = array.length;
while (i--) if (i in array && array[i] === item) return i;
return -1;
};
// Generate an integer Array containing an arithmetic progression. A port of
// the native Python `range()` function. See
// [the Python documentation](http://docs.python.org/library/functions.html#range).
_.range = function(start, stop, step) {
if (arguments.length <= 1) {
stop = start || 0;
start = 0;
}
step = arguments[2] || 1;
var len = Math.max(Math.ceil((stop - start) / step), 0);
var idx = 0;
var range = new Array(len);
while(idx < len) {
range[idx++] = start;
start += step;
}
return range;
};
// Function (ahem) Functions
// ------------------
// Reusable constructor function for prototype setting.
var ctor = function(){};
// Create a function bound to a given object (assigning `this`, and arguments,
// optionally). Binding with arguments is also known as `curry`.
// Delegates to **ECMAScript 5**'s native `Function.bind` if available.
// We check for `func.bind` first, to fail fast when `func` is undefined.
_.bind = function bind(func, context) {
var bound, args;
if (func.bind === nativeBind && nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
if (!_.isFunction(func)) throw new TypeError;
args = slice.call(arguments, 2);
return bound = function() {
if (!(this instanceof bound)) return func.apply(context, args.concat(slice.call(arguments)));
ctor.prototype = func.prototype;
var self = new ctor;
var result = func.apply(self, args.concat(slice.call(arguments)));
if (Object(result) === result) return result;
return self;
};
};
// Bind all of an object's methods to that object. Useful for ensuring that
// all callbacks defined on an object belong to it.
_.bindAll = function(obj) {
var funcs = slice.call(arguments, 1);
if (funcs.length == 0) funcs = _.functions(obj);
each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
return obj;
};
// Memoize an expensive function by storing its results.
_.memoize = function(func, hasher) {
var memo = {};
hasher || (hasher = _.identity);
return function() {
var key = hasher.apply(this, arguments);
return _.has(memo, key) ? memo[key] : (memo[key] = func.apply(this, arguments));
};
};
// Delays a function for the given number of milliseconds, and then calls
// it with the arguments supplied.
_.delay = function(func, wait) {
var args = slice.call(arguments, 2);
return setTimeout(function(){ return func.apply(func, args); }, wait);
};
// Defers a function, scheduling it to run after the current call stack has
// cleared.
_.defer = function(func) {
return _.delay.apply(_, [func, 1].concat(slice.call(arguments, 1)));
};
// Returns a function, that, when invoked, will only be triggered at most once
// during a given window of time.
_.throttle = function(func, wait) {
var context, args, timeout, throttling, more;
var whenDone = _.debounce(function(){ more = throttling = false; }, wait);
return function() {
context = this; args = arguments;
var later = function() {
timeout = null;
if (more) func.apply(context, args);
whenDone();
};
if (!timeout) timeout = setTimeout(later, wait);
if (throttling) {
more = true;
} else {
func.apply(context, args);
}
whenDone();
throttling = true;
};
};
// Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for
// N milliseconds.
_.debounce = function(func, wait) {
var timeout;
return function() {
var context = this, args = arguments;
var later = function() {
timeout = null;
func.apply(context, args);
};
clearTimeout(timeout);
timeout = setTimeout(later, wait);
};
};
// Returns a function that will be executed at most one time, no matter how
// often you call it. Useful for lazy initialization.
_.once = function(func) {
var ran = false, memo;
return function() {
if (ran) return memo;
ran = true;
return memo = func.apply(this, arguments);
};
};
// Returns the first function passed as an argument to the second,
// allowing you to adjust arguments, run code before and after, and
// conditionally execute the original function.
_.wrap = function(func, wrapper) {
return function() {
var args = [func].concat(slice.call(arguments, 0));
return wrapper.apply(this, args);
};
};
// Returns a function that is the composition of a list of functions, each
// consuming the return value of the function that follows.
_.compose = function() {
var funcs = arguments;
return function() {
var args = arguments;
for (var i = funcs.length - 1; i >= 0; i--) {
args = [funcs[i].apply(this, args)];
}
return args[0];
};
};
// Returns a function that will only be executed after being called N times.
_.after = function(times, func) {
if (times <= 0) return func();
return function() {
if (--times < 1) { return func.apply(this, arguments); }
};
};
// Object Functions
// ----------------
// Retrieve the names of an object's properties.
// Delegates to **ECMAScript 5**'s native `Object.keys`
_.keys = nativeKeys || function(obj) {
if (obj !== Object(obj)) throw new TypeError('Invalid object');
var keys = [];
for (var key in obj) if (_.has(obj, key)) keys[keys.length] = key;
return keys;
};
// Retrieve the values of an object's properties.
_.values = function(obj) {
return _.map(obj, _.identity);
};
// Return a sorted list of the function names available on the object.
// Aliased as `methods`
_.functions = _.methods = function(obj) {
var names = [];
for (var key in obj) {
if (_.isFunction(obj[key])) names.push(key);
}
return names.sort();
};
// Extend a given object with all the properties in passed-in object(s).
_.extend = function(obj) {
each(slice.call(arguments, 1), function(source) {
for (var prop in source) {
obj[prop] = source[prop];
}
});
return obj;
};
// Fill in a given object with default properties.
_.defaults = function(obj) {
each(slice.call(arguments, 1), function(source) {
for (var prop in source) {
if (obj[prop] == null) obj[prop] = source[prop];
}
});
return obj;
};
// Create a (shallow-cloned) duplicate of an object.
_.clone = function(obj) {
if (!_.isObject(obj)) return obj;
return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
};
// Invokes interceptor with the obj, and then returns obj.
// The primary purpose of this method is to "tap into" a method chain, in
// order to perform operations on intermediate results within the chain.
_.tap = function(obj, interceptor) {
interceptor(obj);
return obj;
};
// Internal recursive comparison function.
function eq(a, b, stack) {
// Identical objects are equal. `0 === -0`, but they aren't identical.
// See the Harmony `egal` proposal: http://wiki.ecmascript.org/doku.php?id=harmony:egal.
if (a === b) return a !== 0 || 1 / a == 1 / b;
// A strict comparison is necessary because `null == undefined`.
if (a == null || b == null) return a === b;
// Unwrap any wrapped objects.
if (a._chain) a = a._wrapped;
if (b._chain) b = b._wrapped;
// Invoke a custom `isEqual` method if one is provided.
if (a.isEqual && _.isFunction(a.isEqual)) return a.isEqual(b);
if (b.isEqual && _.isFunction(b.isEqual)) return b.isEqual(a);
// Compare `[[Class]]` names.
var className = toString.call(a);
if (className != toString.call(b)) return false;
switch (className) {
// Strings, numbers, dates, and booleans are compared by value.
case '[object String]':
// Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
// equivalent to `new String("5")`.
return a == String(b);
case '[object Number]':
// `NaN`s are equivalent, but non-reflexive. An `egal` comparison is performed for
// other numeric values.
return a != +a ? b != +b : (a == 0 ? 1 / a == 1 / b : a == +b);
case '[object Date]':
case '[object Boolean]':
// Coerce dates and booleans to numeric primitive values. Dates are compared by their
// millisecond representations. Note that invalid dates with millisecond representations
// of `NaN` are not equivalent.
return +a == +b;
// RegExps are compared by their source patterns and flags.
case '[object RegExp]':
return a.source == b.source &&
a.global == b.global &&
a.multiline == b.multiline &&
a.ignoreCase == b.ignoreCase;
}
if (typeof a != 'object' || typeof b != 'object') return false;
// Assume equality for cyclic structures. The algorithm for detecting cyclic
// structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
var length = stack.length;
while (length--) {
// Linear search. Performance is inversely proportional to the number of
// unique nested structures.
if (stack[length] == a) return true;
}
// Add the first object to the stack of traversed objects.
stack.push(a);
var size = 0, result = true;
// Recursively compare objects and arrays.
if (className == '[object Array]') {
// Compare array lengths to determine if a deep comparison is necessary.
size = a.length;
result = size == b.length;
if (result) {
// Deep compare the contents, ignoring non-numeric properties.
while (size--) {
// Ensure commutative equality for sparse arrays.
if (!(result = size in a == size in b && eq(a[size], b[size], stack))) break;
}
}
} else {
// Objects with different constructors are not equivalent.
if ('constructor' in a != 'constructor' in b || a.constructor != b.constructor) return false;
// Deep compare objects.
for (var key in a) {
if (_.has(a, key)) {
// Count the expected number of properties.
size++;
// Deep compare each member.
if (!(result = _.has(b, key) && eq(a[key], b[key], stack))) break;
}
}
// Ensure that both objects contain the same number of properties.
if (result) {
for (key in b) {
if (_.has(b, key) && !(size--)) break;
}
result = !size;
}
}
// Remove the first object from the stack of traversed objects.
stack.pop();
return result;
}
// Perform a deep comparison to check if two objects are equal.
_.isEqual = function(a, b) {
return eq(a, b, []);
};
// Is a given array, string, or object empty?
// An "empty" object has no enumerable own-properties.
_.isEmpty = function(obj) {
if (_.isArray(obj) || _.isString(obj)) return obj.length === 0;
for (var key in obj) if (_.has(obj, key)) return false;
return true;
};
// Is a given value a DOM element?
_.isElement = function(obj) {
return !!(obj && obj.nodeType == 1);
};
// Is a given value an array?
// Delegates to ECMA5's native Array.isArray
_.isArray = nativeIsArray || function(obj) {
return toString.call(obj) == '[object Array]';
};
// Is a given variable an object?
_.isObject = function(obj) {
return obj === Object(obj);
};
// Is a given variable an arguments object?
_.isArguments = function(obj) {
return toString.call(obj) == '[object Arguments]';
};
if (!_.isArguments(arguments)) {
_.isArguments = function(obj) {
return !!(obj && _.has(obj, 'callee'));
};
}
// Is a given value a function?
_.isFunction = function(obj) {
return toString.call(obj) == '[object Function]';
};
// Is a given value a string?
_.isString = function(obj) {
return toString.call(obj) == '[object String]';
};
// Is a given value a number?
_.isNumber = function(obj) {
return toString.call(obj) == '[object Number]';
};
// Is the given value `NaN`?
_.isNaN = function(obj) {
// `NaN` is the only value for which `===` is not reflexive.
return obj !== obj;
};
// Is a given value a boolean?
_.isBoolean = function(obj) {
return obj === true || obj === false || toString.call(obj) == '[object Boolean]';
};
// Is a given value a date?
_.isDate = function(obj) {
return toString.call(obj) == '[object Date]';
};
// Is the given value a regular expression?
_.isRegExp = function(obj) {
return toString.call(obj) == '[object RegExp]';
};
// Is a given value equal to null?
_.isNull = function(obj) {
return obj === null;
};
// Is a given variable undefined?
_.isUndefined = function(obj) {
return obj === void 0;
};
// Has own property?
_.has = function(obj, key) {
return hasOwnProperty.call(obj, key);
};
// Utility Functions
// -----------------
// Run Underscore.js in *noConflict* mode, returning the `_` variable to its
// previous owner. Returns a reference to the Underscore object.
_.noConflict = function() {
root._ = previousUnderscore;
return this;
};
// Keep the identity function around for default iterators.
_.identity = function(value) {
return value;
};
// Run a function **n** times.
_.times = function (n, iterator, context) {
for (var i = 0; i < n; i++) iterator.call(context, i);
};
// Escape a string for HTML interpolation.
_.escape = function(string) {
return (''+string).replace(/&/g, '&').replace(//g, '>').replace(/"/g, '"').replace(/'/g, ''').replace(/\//g,'/');
};
// Add your own custom functions to the Underscore object, ensuring that
// they're correctly added to the OOP wrapper as well.
_.mixin = function(obj) {
each(_.functions(obj), function(name){
addToWrapper(name, _[name] = obj[name]);
});
};
// Generate a unique integer id (unique within the entire client session).
// Useful for temporary DOM ids.
var idCounter = 0;
_.uniqueId = function(prefix) {
var id = idCounter++;
return prefix ? prefix + id : id;
};
// By default, Underscore uses ERB-style template delimiters, change the
// following template settings to use alternative delimiters.
_.templateSettings = {
evaluate : /<%([\s\S]+?)%>/g,
interpolate : /<%=([\s\S]+?)%>/g,
escape : /<%-([\s\S]+?)%>/g
};
// When customizing `templateSettings`, if you don't want to define an
// interpolation, evaluation or escaping regex, we need one that is
// guaranteed not to match.
var noMatch = /.^/;
// Within an interpolation, evaluation, or escaping, remove HTML escaping
// that had been previously added.
var unescape = function(code) {
return code.replace(/\\\\/g, '\\').replace(/\\'/g, "'");
};
// JavaScript micro-templating, similar to John Resig's implementation.
// Underscore templating handles arbitrary delimiters, preserves whitespace,
// and correctly escapes quotes within interpolated code.
_.template = function(str, data) {
var c = _.templateSettings;
var tmpl = 'var __p=[],print=function(){__p.push.apply(__p,arguments);};' +
'with(obj||{}){__p.push(\'' +
str.replace(/\\/g, '\\\\')
.replace(/'/g, "\\'")
.replace(c.escape || noMatch, function(match, code) {
return "',_.escape(" + unescape(code) + "),'";
})
.replace(c.interpolate || noMatch, function(match, code) {
return "'," + unescape(code) + ",'";
})
.replace(c.evaluate || noMatch, function(match, code) {
return "');" + unescape(code).replace(/[\r\n\t]/g, ' ') + ";__p.push('";
})
.replace(/\r/g, '\\r')
.replace(/\n/g, '\\n')
.replace(/\t/g, '\\t')
+ "');}return __p.join('');";
var func = new Function('obj', '_', tmpl);
if (data) return func(data, _);
return function(data) {
return func.call(this, data, _);
};
};
// Add a "chain" function, which will delegate to the wrapper.
_.chain = function(obj) {
return _(obj).chain();
};
// The OOP Wrapper
// ---------------
// If Underscore is called as a function, it returns a wrapped object that
// can be used OO-style. This wrapper holds altered versions of all the
// underscore functions. Wrapped objects may be chained.
var wrapper = function(obj) { this._wrapped = obj; };
// Expose `wrapper.prototype` as `_.prototype`
_.prototype = wrapper.prototype;
// Helper function to continue chaining intermediate results.
var result = function(obj, chain) {
return chain ? _(obj).chain() : obj;
};
// A method to easily add functions to the OOP wrapper.
var addToWrapper = function(name, func) {
wrapper.prototype[name] = function() {
var args = slice.call(arguments);
unshift.call(args, this._wrapped);
return result(func.apply(_, args), this._chain);
};
};
// Add all of the Underscore functions to the wrapper object.
_.mixin(_);
// Add all mutator Array functions to the wrapper.
each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
var method = ArrayProto[name];
wrapper.prototype[name] = function() {
var wrapped = this._wrapped;
method.apply(wrapped, arguments);
var length = wrapped.length;
if ((name == 'shift' || name == 'splice') && length === 0) delete wrapped[0];
return result(wrapped, this._chain);
};
});
// Add all accessor Array functions to the wrapper.
each(['concat', 'join', 'slice'], function(name) {
var method = ArrayProto[name];
wrapper.prototype[name] = function() {
return result(method.apply(this._wrapped, arguments), this._chain);
};
});
// Start chaining a wrapped Underscore object.
wrapper.prototype.chain = function() {
this._chain = true;
return this;
};
// Extracts the result from a wrapped and chained object.
wrapper.prototype.value = function() {
return this._wrapped;
};
}).call(this);
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