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Lib/site-packages/pipenv/vendor/first.py

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+## -*- coding: utf-8 -*-
+
+"""
+first
+=====
+
+first is the function you always missed in Python.
+
+In the simplest case, it returns the first true element from an iterable:
+
+>>> from first import first
+>>> first([0, False, None, [], (), 42])
+42
+
+Or None if there is none:
+
+>>> from first import first
+>>> first([]) is None
+True
+>>> first([0, False, None, [], ()]) is None
+True
+
+It also supports the passing of a key argument to help selecting the first
+match in a more advanced way.
+
+>>> from first import first
+>>> first([1, 1, 3, 4, 5], key=lambda x: x % 2 == 0)
+4
+
+:copyright: (c) 2012 by Hynek Schlawack.
+:license: MIT, see LICENSE for more details.
+
+"""
+
+__title__ = 'first'
+__version__ = '2.0.1'
+__author__ = 'Hynek Schlawack'
+__license__ = 'MIT'
+__copyright__ = 'Copyright 2012–2013 Hynek Schlawack'
+
+
+def first(iterable, default=None, key=None):
+    """
+    Return first element of `iterable` that evaluates true, else return None
+    (or an optional default value).
+
+    >>> first([0, False, None, [], (), 42])
+    42
+
+    >>> first([0, False, None, [], ()]) is None
+    True
+
+    >>> first([0, False, None, [], ()], default='ohai')
+    'ohai'
+
+    >>> import re
+    >>> m = first(re.match(regex, 'abc') for regex in ['b.*', 'a(.*)'])
+    >>> m.group(1)
+    'bc'
+
+    The optional `key` argument specifies a one-argument predicate function
+    like that used for `filter()`.  The `key` argument, if supplied, must be
+    in keyword form.  For example:
+
+    >>> first([1, 1, 3, 4, 5], key=lambda x: x % 2 == 0)
+    4
+
+    """
+    if key is None:
+        for el in iterable:
+            if el:
+                return el
+    else:
+        for el in iterable:
+            if key(el):
+                return el
+
+    return default