Viewing file:  fix_division_safe.py (3.38 KB) -rw-r--r--
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"""
For the ``future`` package.
Adds this import line:
from __future__ import division
at the top and changes any old-style divisions to be calls to
past.utils.old_div so the code runs as before on Py2.6/2.7 and has the same
behaviour on Py3.
If "from __future__ import division" is already in effect, this fixer does
nothing.
"""
import re
import lib2to3.pytree as pytree
from lib2to3.fixer_util import Leaf, Node, Comma
from lib2to3 import fixer_base
from lib2to3.fixer_util import syms, does_tree_import
from libfuturize.fixer_util import (token, future_import, touch_import_top,
wrap_in_fn_call)
def match_division(node):
u"""
__future__.division redefines the meaning of a single slash for division,
so we match that and only that.
"""
slash = token.SLASH
return node.type == slash and not node.next_sibling.type == slash and \
not node.prev_sibling.type == slash
const_re = re.compile('^[0-9]*[.][0-9]*$')
def is_floaty(node, div_idx):
return _is_floaty(node.children[0:div_idx]) or _is_floaty(node.children[div_idx+1:])
def _is_floaty(expr):
if isinstance(expr, list):
expr = expr[0]
if isinstance(expr, Leaf):
# If it's a leaf, let's see if it's a numeric constant containing a '.'
return const_re.match(expr.value)
elif isinstance(expr, Node):
# If the expression is a node, let's see if it's a direct cast to float
if isinstance(expr.children[0], Leaf):
return expr.children[0].value == u'float'
return False
def find_division(node):
for i, child in enumerate(node.children):
if match_division(child):
return i
return False
def clone_div_operands(node, div_idx):
children = []
for i, child in enumerate(node.children):
if i == div_idx:
children.append(Comma())
else:
children.append(child.clone())
# Strip any leading space for the first number:
children[0].prefix = u''
return children
class FixDivisionSafe(fixer_base.BaseFix):
# BM_compatible = True
run_order = 4 # this seems to be ignored?
_accept_type = token.SLASH
PATTERN = """
term<(not('/') any)+ '/' ((not('/') any))>
"""
def start_tree(self, tree, name):
"""
Skip this fixer if "__future__.division" is already imported.
"""
super(FixDivisionSafe, self).start_tree(tree, name)
self.skip = "division" in tree.future_features
def match(self, node):
u"""
Since the tree needs to be fixed once and only once if and only if it
matches, we can start discarding matches after the first.
"""
if node.type == self.syms.term:
div_idx = find_division(node)
if div_idx is not False:
# if expr1 or expr2 are obviously floats, we don't need to wrap in
# old_div, as the behavior of division between any number and a float
# should be the same in 2 or 3
if not is_floaty(node, div_idx):
return clone_div_operands(node, div_idx)
return False
def transform(self, node, results):
if self.skip:
return
future_import(u"division", node)
touch_import_top(u'past.utils', u'old_div', node)
return wrap_in_fn_call("old_div", results, prefix=node.prefix)
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