186 lines
4.3 KiB
Python
186 lines
4.3 KiB
Python
"""
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Compatibility constants and functions. This module works on Python 1.5 to 2.5.
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This module provides:
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- True and False constants ;
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- any() and all() function ;
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- has_yield and has_slice values ;
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- isinstance() with Python 2.3 behaviour ;
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- reversed() and sorted() function.
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True and False constants
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========================
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Truth constants: True is yes (one) and False is no (zero).
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>>> int(True), int(False) # int value
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(1, 0)
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>>> int(False | True) # and binary operator
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1
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>>> int(True & False) # or binary operator
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0
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>>> int(not(True) == False) # not binary operator
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1
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Warning: on Python smaller than 2.3, True and False are aliases to
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number 1 and 0. So "print True" will displays 1 and not True.
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any() function
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==============
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any() returns True if at least one items is True, or False otherwise.
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>>> any([False, True])
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True
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>>> any([True, True])
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True
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>>> any([False, False])
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False
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all() function
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==============
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all() returns True if all items are True, or False otherwise.
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This function is just apply binary and operator (&) on all values.
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>>> all([True, True])
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True
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>>> all([False, True])
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False
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>>> all([False, False])
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False
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has_yield boolean
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=================
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has_yield: boolean which indicatese if the interpreter supports yield keyword.
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yield keyworkd is available since Python 2.0.
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has_yield boolean
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=================
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has_slice: boolean which indicates if the interpreter supports slices with step
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argument or not. slice with step is available since Python 2.3.
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reversed() and sorted() function
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================================
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reversed() and sorted() function has been introduced in Python 2.4.
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It's should returns a generator, but this module it may be a list.
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>>> data = list("cab")
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>>> list(sorted(data))
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['a', 'b', 'c']
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>>> list(reversed("abc"))
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['c', 'b', 'a']
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"""
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import copy
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import operator
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# --- True and False constants from Python 2.0 ---
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# --- Warning: for Python < 2.3, they are aliases for 1 and 0 ---
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try:
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True = True
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False = False
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except NameError:
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True = 1
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False = 0
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# --- any() from Python 2.5 ---
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try:
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from __builtin__ import any
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except ImportError:
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def any(items):
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for item in items:
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if item:
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return True
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return False
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# ---all() from Python 2.5 ---
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try:
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from __builtin__ import all
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except ImportError:
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def all(items):
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return reduce(operator.__and__, items)
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# --- test if interpreter supports yield keyword ---
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try:
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eval(compile("""
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from __future__ import generators
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def gen():
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yield 1
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yield 2
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if list(gen()) != [1, 2]:
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raise KeyError("42")
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""", "<string>", "exec"))
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except (KeyError, SyntaxError):
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has_yield = False
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else:
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has_yield = True
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# --- test if interpreter supports slices (with step argument) ---
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try:
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has_slice = eval('"abc"[::-1] == "cba"')
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except (TypeError, SyntaxError):
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has_slice = False
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# --- isinstance with isinstance Python 2.3 behaviour (arg 2 is a type) ---
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try:
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if isinstance(1, int):
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from __builtin__ import isinstance
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except TypeError:
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print "Redef isinstance"
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def isinstance20(a, typea):
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if type(typea) != type(type):
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raise TypeError("TypeError: isinstance() arg 2 must be a class, type, or tuple of classes and types")
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return type(typea) != typea
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isinstance = isinstance20
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# --- reversed() from Python 2.4 ---
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try:
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from __builtin__ import reversed
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except ImportError:
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# if hasYield() == "ok":
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# code = """
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#def reversed(data):
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# for index in xrange(len(data)-1, -1, -1):
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# yield data[index];
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#reversed"""
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# reversed = eval(compile(code, "<string>", "exec"))
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if has_slice:
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def reversed(data):
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if not isinstance(data, list):
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data = list(data)
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return data[::-1]
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else:
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def reversed(data):
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if not isinstance(data, list):
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data = list(data)
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reversed_data = []
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for index in xrange(len(data)-1, -1, -1):
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reversed_data.append(data[index])
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return reversed_data
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# --- sorted() from Python 2.4 ---
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try:
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from __builtin__ import sorted
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except ImportError:
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def sorted(data):
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sorted_data = copy.copy(data)
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sorted_data.sort()
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return sorted
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__all__ = ("True", "False",
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"any", "all", "has_yield", "has_slice",
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"isinstance", "reversed", "sorted")
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