Source code for sympy.core.compatibility

Reimplementations of constructs introduced in later versions of Python than
we support. Also some functions that are needed SymPy-wide and are located
here for easy import.
from __future__ import print_function, division

import operator
from collections import defaultdict
from sympy.external import import_module

Python 2 and Python 3 compatible imports

String and Unicode compatible changes:
    * `unicode()` removed in Python 3, import `unicode` for Python 2/3
      compatible function
    * `unichr()` removed in Python 3, import `unichr` for Python 2/3 compatible
    * Use `u()` for escaped unicode sequences (e.g. u'\u2020' -> u('\u2020'))
    * Use `u_decode()` to decode utf-8 formatted unicode strings
    * `string_types` gives str in Python 3, unicode and str in Python 2,
      equivalent to basestring

Integer related changes:
    * `long()` removed in Python 3, import `long` for Python 2/3 compatible
    * `integer_types` gives int in Python 3, int and long in Python 2

Types related changes:
    * `class_types` gives type in Python 3, type and ClassType in Python 2

Renamed function attributes:
    * Python 2 `.func_code`, Python 3 `.__func__`, access with
    * Python 2 `.func_globals`, Python 3 `.__globals__`, access with
    * Python 2 `.func_name`, Python 3 `.__name__`, access with

Moved modules:
    * `reduce()`
    * `StringIO()`
    * `cStringIO()` (same as `StingIO()` in Python 3)
    * Python 2 `__builtins__`, access with Python 3 name, `builtins`

Iterator/list changes:
    * `xrange` removed in Python 3, import `xrange` for Python 2/3 compatible
      iterator version of range

    * Use `exec_()`, with parameters `exec_(code, globs=None, locs=None)`

    * Use `with_metaclass()`, examples below
        * Define class `Foo` with metaclass `Meta`, and no parent:
            class Foo(with_metaclass(Meta)):
        * Define class `Foo` with metaclass `Meta` and parent class `Bar`:
            class Foo(with_metaclass(Meta, Bar)):

import sys
PY3 = sys.version_info[0] > 2

if PY3:
    class_types = type,
    integer_types = (int,)
    string_types = (str,)
    long = int

    # String / unicode compatibility
    unicode = str
    unichr = chr
    def u(x):
        return x
    def u_decode(x):
        return x

    Iterator = object

    # Moved definitions
    get_function_code = operator.attrgetter("__code__")
    get_function_globals = operator.attrgetter("__globals__")
    get_function_name = operator.attrgetter("__name__")

    import builtins
    from functools import reduce
    from io import StringIO
    cStringIO = StringIO

    exec_ = getattr(builtins, "exec")

    xrange = range
    import codecs
    import types

    class_types = (type, types.ClassType)
    integer_types = (int, long)
    string_types = (str, unicode)
    long = long

    # String / unicode compatibility
    unicode = unicode
    unichr = unichr
    def u(x):
        return codecs.unicode_escape_decode(x)[0]
    def u_decode(x):
        return x.decode('utf-8')

    class Iterator(object):
        def next(self):
            return type(self).__next__(self)

    # Moved definitions
    get_function_code = operator.attrgetter("func_code")
    get_function_globals = operator.attrgetter("func_globals")
    get_function_name = operator.attrgetter("func_name")

    import __builtin__ as builtins
    reduce = reduce
    from StringIO import StringIO
    from cStringIO import StringIO as cStringIO

    def exec_(_code_, _globs_=None, _locs_=None):
        """Execute code in a namespace."""
        if _globs_ is None:
            frame = sys._getframe(1)
            _globs_ = frame.f_globals
            if _locs_ is None:
                _locs_ = frame.f_locals
            del frame
        elif _locs_ is None:
            _locs_ = _globs_
        exec("exec _code_ in _globs_, _locs_")

    xrange = xrange

def with_metaclass(meta, *bases):
    Create a base class with a metaclass.

    For example, if you have the metaclass

    >>> class Meta(type):
    ...     pass

    Use this as the metaclass by doing

    >>> from sympy.core.compatibility import with_metaclass
    >>> class MyClass(with_metaclass(Meta, object)):
    ...     pass

    This is equivalent to the Python 2::

        class MyClass(object):
            __metaclass__ = Meta

    or Python 3::

        class MyClass(object, metaclass=Meta):

    That is, the first argument is the metaclass, and the remaining arguments
    are the base classes. Note that if the base class is just ``object``, you
    may omit it.

    >>> MyClass.__mro__
    (<class 'MyClass'>, <... 'object'>)
    >>> type(MyClass)
    <class 'Meta'>

    class metaclass(meta):
        __call__ = type.__call__
        __init__ = type.__init__
        def __new__(cls, name, this_bases, d):
            if this_bases is None:
                return type.__new__(cls, name, (), d)
            return meta(name, bases, d)
    return metaclass("NewBase", None, {})

# These are in here because telling if something is an iterable just by calling
# hasattr(obj, "__iter__") behaves differently in Python 2 and Python 3.  In
# particular, hasattr(str, "__iter__") is False in Python 2 and True in Python 3.
# I think putting them here also makes it easier to use them in the core.

[docs]def iterable(i, exclude=(string_types, dict)): """ Return a boolean indicating whether ``i`` is SymPy iterable. When SymPy is working with iterables, it is almost always assuming that the iterable is not a string or a mapping, so those are excluded by default. If you want a pure Python definition, make exclude=None. To exclude multiple items, pass them as a tuple. See also: is_sequence Examples ======== >>> from sympy.utilities.iterables import iterable >>> from sympy import Tuple >>> things = [[1], (1,), set([1]), Tuple(1), (j for j in [1, 2]), {1:2}, '1', 1] >>> for i in things: ... print('%s %s' % (iterable(i), type(i))) True <... 'list'> True <... 'tuple'> True <... 'set'> True <class 'sympy.core.containers.Tuple'> True <... 'generator'> False <... 'dict'> False <... 'str'> False <... 'int'> >>> iterable({}, exclude=None) True >>> iterable({}, exclude=str) True >>> iterable("no", exclude=str) False """ try: iter(i) except TypeError: return False if exclude: return not isinstance(i, exclude) return True
[docs]def is_sequence(i, include=None): """ Return a boolean indicating whether ``i`` is a sequence in the SymPy sense. If anything that fails the test below should be included as being a sequence for your application, set 'include' to that object's type; multiple types should be passed as a tuple of types. Note: although generators can generate a sequence, they often need special handling to make sure their elements are captured before the generator is exhausted, so these are not included by default in the definition of a sequence. See also: iterable Examples ======== >>> from sympy.utilities.iterables import is_sequence >>> from types import GeneratorType >>> is_sequence([]) True >>> is_sequence(set()) False >>> is_sequence('abc') False >>> is_sequence('abc', include=str) True >>> generator = (c for c in 'abc') >>> is_sequence(generator) False >>> is_sequence(generator, include=(str, GeneratorType)) True """ return (hasattr(i, '__getitem__') and iterable(i) or bool(include) and isinstance(i, include))
try: from functools import cmp_to_key except ImportError: # <= Python 2.6 def cmp_to_key(mycmp): """ Convert a cmp= function into a key= function """ class K(object): def __init__(self, obj, *args): self.obj = obj def __lt__(self, other): return mycmp(self.obj, other.obj) < 0 def __gt__(self, other): return mycmp(self.obj, other.obj) > 0 def __eq__(self, other): return mycmp(self.obj, other.obj) == 0 def __le__(self, other): return mycmp(self.obj, other.obj) <= 0 def __ge__(self, other): return mycmp(self.obj, other.obj) >= 0 def __ne__(self, other): return mycmp(self.obj, other.obj) != 0 return K try: from itertools import zip_longest except ImportError: # <= Python 2.7 from itertools import izip_longest as zip_longest try: from itertools import combinations_with_replacement except ImportError: # <= Python 2.6 def combinations_with_replacement(iterable, r): """Return r length subsequences of elements from the input iterable allowing individual elements to be repeated more than once. Combinations are emitted in lexicographic sort order. So, if the input iterable is sorted, the combination tuples will be produced in sorted order. Elements are treated as unique based on their position, not on their value. So if the input elements are unique, the generated combinations will also be unique. See also: combinations Examples ======== >>> from sympy.core.compatibility import combinations_with_replacement >>> list(combinations_with_replacement('AB', 2)) [('A', 'A'), ('A', 'B'), ('B', 'B')] """ pool = tuple(iterable) n = len(pool) if not n and r: return indices = [0] * r yield tuple(pool[i] for i in indices) while True: for i in reversed(range(r)): if indices[i] != n - 1: break else: return indices[i:] = [indices[i] + 1] * (r - i) yield tuple(pool[i] for i in indices)
[docs]def as_int(n): """ Convert the argument to a builtin integer. The return value is guaranteed to be equal to the input. ValueError is raised if the input has a non-integral value. Examples ======== >>> from sympy.core.compatibility import as_int >>> from sympy import sqrt >>> 3.0 3.0 >>> as_int(3.0) # convert to int and test for equality 3 >>> int(sqrt(10)) 3 >>> as_int(sqrt(10)) Traceback (most recent call last): ... ValueError: ... is not an integer """ try: result = int(n) if result != n: raise TypeError except TypeError: raise ValueError('%s is not an integer' % n) return result
def default_sort_key(item, order=None): """Return a key that can be used for sorting. The key has the structure: (class_key, (len(args), args), exponent.sort_key(), coefficient) This key is supplied by the sort_key routine of Basic objects when ``item`` is a Basic object or an object (other than a string) that sympifies to a Basic object. Otherwise, this function produces the key. The ``order`` argument is passed along to the sort_key routine and is used to determine how the terms *within* an expression are ordered. (See examples below) ``order`` options are: 'lex', 'grlex', 'grevlex', and reversed values of the same (e.g. 'rev-lex'). The default order value is None (which translates to 'lex'). Examples ======== >>> from sympy import S, I, default_sort_key >>> from sympy.core.function import UndefinedFunction >>> from sympy.abc import x The following are eqivalent ways of getting the key for an object: >>> x.sort_key() == default_sort_key(x) True Here are some examples of the key that is produced: >>> default_sort_key(UndefinedFunction('f')) ((0, 0, 'UndefinedFunction'), (1, ('f',)), ((1, 0, 'Number'), (0, ()), (), 1), 1) >>> default_sort_key('1') ((0, 0, 'str'), (1, ('1',)), ((1, 0, 'Number'), (0, ()), (), 1), 1) >>> default_sort_key(S.One) ((1, 0, 'Number'), (0, ()), (), 1) >>> default_sort_key(2) ((1, 0, 'Number'), (0, ()), (), 2) While sort_key is a method only defined for SymPy objects, default_sort_key will accept anything as an argument so it is more robust as a sorting key. For the following, using key= lambda i: i.sort_key() would fail because 2 doesn't have a sort_key method; that's why default_sort_key is used. Note, that it also handles sympification of non-string items likes ints: >>> a = [2, I, -I] >>> sorted(a, key=default_sort_key) [2, -I, I] The returned key can be used anywhere that a key can be specified for a function, e.g. sort, min, max, etc...: >>> a.sort(key=default_sort_key); a[0] 2 >>> min(a, key=default_sort_key) 2 Note ---- The key returned is useful for getting items into a canonical order that will be the same across platforms. It is not directly useful for sorting lists of expressions: >>> a, b = x, 1/x Since ``a`` has only 1 term, its value of sort_key is unaffected by ``order``: >>> a.sort_key() == a.sort_key('rev-lex') True If ``a`` and ``b`` are combined then the key will differ because there are terms that can be ordered: >>> eq = a + b >>> eq.sort_key() == eq.sort_key('rev-lex') False >>> eq.as_ordered_terms() [x, 1/x] >>> eq.as_ordered_terms('rev-lex') [1/x, x] But since the keys for each of these terms are independent of ``order``'s value, they don't sort differently when they appear separately in a list: >>> sorted(eq.args, key=default_sort_key) [1/x, x] >>> sorted(eq.args, key=lambda i: default_sort_key(i, order='rev-lex')) [1/x, x] The order of terms obtained when using these keys is the order that would be obtained if those terms were *factors* in a product. See Also ======== sympy.core.expr.as_ordered_factors, sympy.core.expr.as_ordered_terms """ from sympy.core import S, Basic from sympy.core.sympify import sympify, SympifyError from sympy.core.compatibility import iterable if isinstance(item, Basic): return item.sort_key(order=order) if iterable(item, exclude=string_types): if isinstance(item, dict): args = item.items() unordered = True elif isinstance(item, set): args = item unordered = True else: # e.g. tuple, list args = list(item) unordered = False args = [default_sort_key(arg, order=order) for arg in args] if unordered: # e.g. dict, set args = sorted(args) cls_index, args = 10, (len(args), tuple(args)) else: if not isinstance(item, string_types): try: item = sympify(item) except SympifyError: # e.g. lambda x: x pass else: if isinstance(item, Basic): # e.g int -> Integer return default_sort_key(item) # e.g. UndefinedFunction # e.g. str cls_index, args = 0, (1, (str(item),)) return (cls_index, 0, item.__class__.__name__ ), args, S.One.sort_key(), S.One def _nodes(e): """ A helper for ordered() which returns the node count of ``e`` which for Basic object is the number of Basic nodes in the expression tree but for other object is 1 (unless the object is an iterable or dict for which the sum of nodes is returned). """ from .basic import Basic if isinstance(e, Basic): return e.count(Basic) elif iterable(e): return 1 + sum(_nodes(ei) for ei in e) elif isinstance(e, dict): return 1 + sum(_nodes(k) + _nodes(v) for k, v in e.items()) else: return 1 def ordered(seq, keys=None, default=True, warn=False): """Return an iterator of the seq where keys are used to break ties. Two default keys will be applied after and provided unless ``default`` is False. The two keys are _nodes and default_sort_key which will place smaller expressions before larger ones (in terms of Basic nodes) and where there are ties, they will be broken by the default_sort_key. If ``warn`` is True then an error will be raised if there were no keys remaining to break ties. This can be used if it was expected that there should be no ties. Examples ======== >>> from sympy.utilities.iterables import ordered >>> from sympy import count_ops >>> from sympy.abc import x, y The count_ops is not sufficient to break ties in this list and the first two items appear in their original order (i.e. the sorting is stable): >>> list(ordered([y + 2, x + 2, x**2 + y + 3], ... count_ops, default=False, warn=False)) ... [y + 2, x + 2, x**2 + y + 3] The default_sort_key allows the tie to be broken: >>> list(ordered([y + 2, x + 2, x**2 + y + 3])) ... [x + 2, y + 2, x**2 + y + 3] Here, sequences are sorted by length, then sum: >>> seq, keys = [[[1, 2, 1], [0, 3, 1], [1, 1, 3], [2], [1]], [ ... lambda x: len(x), ... lambda x: sum(x)]] ... >>> list(ordered(seq, keys, default=False, warn=False)) [[1], [2], [1, 2, 1], [0, 3, 1], [1, 1, 3]] If ``warn`` is True, an error will be raised if there were not enough keys to break ties: >>> list(ordered(seq, keys, default=False, warn=True)) Traceback (most recent call last): ... ValueError: not enough keys to break ties Notes ===== The decorated sort is one of the fastest ways to sort a sequence for which special item comparison is desired: the sequence is decorated, sorted on the basis of the decoration (e.g. making all letters lower case) and then undecorated. If one wants to break ties for items that have the same decorated value, a second key can be used. But if the second key is expensive to compute then it is inefficient to decorate all items with both keys: only those items having identical first key values need to be decorated. This function applies keys successively only when needed to break ties. By yielding an iterator, use of the tie-breaker is delayed as long as possible. This function is best used in cases when use of the first key is expected to be a good hashing function; if there are no unique hashes from application of a key then that key should not have been used. The exception, however, is that even if there are many collisions, if the first group is small and one does not need to process all items in the list then time will not be wasted sorting what one was not interested in. For example, if one were looking for the minimum in a list and there were several criteria used to define the sort order, then this function would be good at returning that quickly if the first group of candidates is small relative to the number of items being processed. """ d = defaultdict(list) if keys: if not isinstance(keys, (list, tuple)): keys = [keys] keys = list(keys) f = keys.pop(0) for a in seq: d[f(a)].append(a) else: if not default: raise ValueError('if default=False then keys must be provided') d[None].extend(seq) for k in sorted(d.keys()): if len(d[k]) > 1: if keys: d[k] = ordered(d[k], keys, default, warn) elif default: d[k] = ordered(d[k], (_nodes, default_sort_key,), default=False, warn=warn) elif warn: raise ValueError('not enough keys to break ties') for v in d[k]: yield v d.pop(k) # If HAS_GMPY is 0, no supported version of gmpy is available. Otherwise, # HAS_GMPY contains the major version number of gmpy; i.e. 1 for gmpy, and # 2 for gmpy2. # Versions of gmpy prior to 1.03 do not work correctly with int(largempz) # For example, int(gmpy.mpz(2**256)) would raise OverflowError. # See issue 1881. # Minimum version of gmpy changed to 1.13 to allow a single code base to also # work with gmpy2. def _getenv(key, default=None): from os import getenv return getenv(key, default) GROUND_TYPES = _getenv('SYMPY_GROUND_TYPES', 'auto').lower() HAS_GMPY = 0 if GROUND_TYPES != 'python': # Don't try to import gmpy2 if ground types is set to gmpy1. This is # primarily intended for testing. if GROUND_TYPES != 'gmpy1': gmpy = import_module('gmpy2', min_module_version='2.0.0', module_version_attr='version', module_version_attr_call_args=()) if gmpy: HAS_GMPY = 2 else: GROUND_TYPES = 'gmpy' if not HAS_GMPY: gmpy = import_module('gmpy', min_module_version='1.13', module_version_attr='version', module_version_attr_call_args=()) if gmpy: HAS_GMPY = 1 if GROUND_TYPES == 'auto': if HAS_GMPY: GROUND_TYPES = 'gmpy' else: GROUND_TYPES = 'python' if GROUND_TYPES == 'gmpy' and not HAS_GMPY: from warnings import warn warn("gmpy library is not installed, switching to 'python' ground types") GROUND_TYPES = 'python' # SYMPY_INTS is a tuple containing the base types for valid integer types. SYMPY_INTS = integer_types if GROUND_TYPES == 'gmpy': SYMPY_INTS += (type(gmpy.mpz(0)),) # check_output() is new in Python 2.7 import os try: try: from subprocess import check_output except ImportError: # <= Python 2.6 from subprocess import CalledProcessError, check_call def check_output(*args, **kwargs): with open(os.devnull, 'w') as fh: kwargs['stdout'] = fh try: return check_call(*args, **kwargs) except CalledProcessError as e: e.output = ("program output is not available for Python 2.6.x") raise e except ImportError: # running on platform like App Engine, no subprocess at all pass