src/pyprimes/compat23.py

   1 # -*- coding: utf-8 -*-
   2
   3 ##  Part of the pyprimes.py package.
   4 ##
   5 ##  Copyright © 2014 Steven D'Aprano.
   6 ##  See the file __init__.py for the licence terms for this software.
   7
   8
   9 """Python 2 and 3 compatibility layer for the pyprimes package.
  10
  11 This module is considered a private implementation detail and is subject
  12 to change without notice.
  13 """
  14
  15 from __future__ import division
  16
  17
  18 try:
  19     import builtins  # Python 3.x.
  20 except ImportError:
  21     # We're probably running Python 2.x.
  22     import __builtin__ as builtins
  23
  24
  25 try:
  26     next = builtins.next
  27 except AttributeError:
  28     # No next() builtin, so we're probably running Python 2.4 or 2.5.
  29     def next(iterator, *args):
  30         if len(args) > 1:
  31             n = len(args) + 1
  32             raise TypeError("next expected at most 2 arguments, got %d" % n)
  33         try:
  34             return iterator.next()
  35         except StopIteration:
  36             if args:
  37                 return args[0]
  38             else:
  39                 raise
  40
  41
  42 try:
  43     range = builtins.xrange
  44 except AttributeError:
  45     # No xrange built-in, so we're probably running Python3
  46     # where range is already a lazy iterator.
  47     assert type(builtins.range(3)) is not list
  48     range = builtins.range
  49
  50
  51 try:
  52     from itertools import ifilter as filter, izip as zip
  53 except ImportError:
  54     # Python 3, where filter and zip are already lazy.
  55     assert type(builtins.filter(None, [1, 2])) is not list
  56     assert type(builtins.zip("ab", [1, 2])) is not list
  57     filter = builtins.filter
  58     zip = builtins.zip
  59
  60
  61 try:
  62     all = builtins.all
  63 except AttributeError:
  64     # Likely Python 2.4.
  65     def all(iterable):
  66         for element in iterable:
  67             if not element:
  68                 return False
  69         return True
  70
  71
  72 try:
  73     from itertools import compress
  74 except ImportError:
  75     # Must be Python 2.x, so we need to roll our own.
  76     def compress(data, selectors):
  77         """compress('ABCDEF', [1,0,1,0,1,1]) --> A C E F"""
  78         return (d for d, s in zip(data, selectors) if s)
  79
  80
  81 try:
  82     reduce = builtins.reduce
  83 except AttributeError:
  84     from functools import reduce
  85
  86