bebraw
1/10/2010 - 12:37 PM
assignment.py
import re
class Assignment:
def matches(self, expression):
'''
>>> assignment = Assignment()
>>> assignment.matches('a=5')
True
>>> assignment.matches(' a = 5 ')
True
>>> assignment.matches('5=5')
False
Extra whitespace in name
>>> assignment.matches('bar bar = 5')
False
Assignment of a variable's value
>>> assignment.matches('a=b')
True
Underscore is allowed in the beginning
>>> assignment.matches('_fooDOO=bar')
True
>>> assignment.matches('a=b+5')
True
Multiple assignment
>>> assignment.matches('a=b=5')
True
Multipart
>>> assignment.matches('a, b = 5, 10')
True
>>> assignment.matches('a, b, c = 5, 10')
False
Multiple assignment and multipart
>>> assignment.matches('a, b = d, e = 10, 13')
True
Disallow minus in front of a name because "foo - -FOO" is
ambiguous
>>> assignment.matches('-FOO=b')
False
>>> assignment.matches('a, -b = 5, 10')
False
Disallow minus in middle of a name because "foo-doo" is
ambiguous
>>> assignment.matches('foo-doo=b')
False
Don't match if missing =
>>> assignment.matches('a + b')
False
Don't match empty
>>> assignment.matches('')
False
- expansion
>>> assignment.matches('FOO-=b')
True
+ expansion
>>> assignment.matches('FOO+=b')
True
* expansion
>>> assignment.matches('FOO*=b')
True
/ expansion
>>> assignment.matches('FOO/=b')
True
% expansion
>>> assignment.matches('FOO%=b')
True
'''
parts = self._split_expression(expression)
if len(parts) < 2:
return False
first_segments_len = len(parts[0].segments)
for part in parts:
if len(part.segments) != first_segments_len:
return False
if len(parts) == 2 and len(parts[0].segments) == 1:
l_part = parts[0].segments[0]
if not l_part.is_valid():
return False
else:
for part in parts[:-1]:
for segment in part.segments:
if not segment.is_valid():
return False
return True
def execute(self, expression, commands, variables):
'''
>>> from mock import Mock
>>> from py.test import raises
>>> python = Mock()
>>> commands = Mock()
>>> commands.find.return_value = python
>>> assignment = Assignment()
Simple assignment
>>> python.execute.return_value = 5
>>> variables = {}
>>> assignment.execute('a=5', commands, variables)
>>> variables
{'a': 5}
Multipart
>>> python.execute.return_value = 5
>>> variables = {}
>>> assignment.execute('a=b=5', commands, variables)
>>> variables
{'a': 5, 'b': 5}
Multiple assignment
TODO: check type conversion (int to str?)
>>> def execute(expression, variables):
... return expression
>>> python.execute = execute
>>> variables = {}
>>> assignment.execute('a, b = 5, 10', commands, variables)
>>> variables
{'a': '5', 'b': '10'}
Multiple assignment and multipart
TODO: check type conversion (int to str?)
>>> def execute(expression, variables):
... return expression
>>> python.execute = execute
>>> variables = {'a': 5, 'b': 6}
>>> assignment.execute('a, b = c, d = 5, 10', commands, variables)
>>> variables
{'a': '5', 'c': '5', 'b': '10', 'd': '10'}
Assignment of the value of another variable
>>> python.execute = Mock()
>>> python.execute.return_value = 10
>>> variables = {'a': 10}
>>> assignment.execute('b=a', commands, variables)
>>> variables
{'a': 10, 'b': 10}
Assignment of a result
>>> python.execute.return_value = 15
>>> variables = {'a': 10}
>>> assignment.execute('b=a+5', commands, variables)
>>> variables
{'a': 10, 'b': 15}
- expansion
>>> python.execute.return_value = 5
>>> variables = {'a': 10}
>>> assignment.execute('a-=5', commands, variables)
>>> variables
{'a': 5}
+ expansion
>>> python.execute.return_value = 15
>>> variables = {'a': 10}
>>> assignment.execute('a+=5', commands, variables)
>>> variables
{'a': 15}
* expansion
>>> python.execute.return_value = 50
>>> variables = {'a': 10}
>>> assignment.execute('a*=5', commands, variables)
>>> variables
{'a': 50}
/ expansion
>>> python.execute.return_value = 2
>>> variables = {'a': 10}
>>> assignment.execute('a/=5', commands, variables)
>>> variables
{'a': 2}
% expansion
>>> python.execute.return_value = 0
>>> variables = {'a': 10}
>>> assignment.execute('a%=5', commands, variables)
>>> variables
{'a': 0}
Assignment of an invalid variable
>>> python.execute = Mock()
>>> python.execute.side_effect = NameError("name 'b' is not defined")
>>> variables = {}
>>> exception = raises(NameError, assignment.execute, 'a=b', commands,
... variables)
>>> exception.typename
'NameError'
>>> variables
{}
Assignment of an invalid variable - Multipart case
>>> python.execute = Mock()
>>> python.execute.side_effect = NameError("name 'c' is not defined")
>>> variables = {}
>>> exception = raises(NameError, assignment.execute, 'a=b=c',
... commands, variables)
>>> exception.typename
'NameError'
>>> variables
{}
Assignment of an invalid variable - Multiple assignment case
>>> python.execute = Mock()
>>> python.execute.side_effect = NameError("name 'c' is not defined")
>>> variables = {}
>>> exception = raises(NameError, assignment.execute, 'a,b=c,d',
... commands, variables)
>>> exception.typename
'NameError'
>>> variables
{}
'''
def set_variables(l_part, r_part):
python = commands.find('python')
for l_segment, r_segment in zip(l_part.segments, r_part.segments):
if r_segment in variables:
variables[l_segment] = variables[r_segment]
else:
variables[l_segment] = python.execute(r_segment, variables)
parts = self._split_expression(expression)
if len(parts) == 2:
if len(parts[1].segments) == 1:
parts[1].expand(parts[0])
ret = set_variables(parts[0], parts[1])
return ret
else:
for l_part in parts[:-1]:
ret = set_variables(l_part, parts[-1])
if ret:
return ret
def _split_expression(self, expression):
class Segment(str):
def is_valid(self):
return re.match('^[a-zA-Z_]{1}[a-zA-Z_]*$', self)
class Part:
def __init__(self, value):
value = value.strip()
if len(value) > 0 and value[-1] in ('+', '-', '*', '/', '%'):
self.expansion = value[-1]
self.segments = (Segment(value[:-1]), )
else:
self.expansion = None
self.segments = (Segment(value), )
def expand(self, l_part):
expansion = l_part.expansion
if expansion:
self.segments = (l_part.segments[0] + expansion + \
self.segments[0], )
class SegmentedPart:
def __init__(self, raw_part):
segments = raw_part.split(',')
self.segments = []
for segment in segments:
self.segments.append(Segment(segment.strip()))
expression = expression.strip()
parts = expression.split('=')
ret = []
for part in parts:
if part.count(',') > 0:
ret.append(SegmentedPart(part))
else:
ret.append(Part(part))
return ret
if __name__ == "__main__":
import doctest
doctest.testmod()