convert string to pre defined python variable

Question

I wanted to know How can I convert string to python defined variables.

Basically I want to do this.

if value1 operator value2:
 print True 

my operator is a string '==' , '>', '<', '!=' so that it becomes

if value1 == value2:
 print True

I tried operator = getattr(sys.modules[__name__], operator ) but it work for class. thanks.

• Andrew Jaffe: The question is fine, but the title isn't very clear.

Answer 1

Using the operator module:

import operator
def op(str, value1, value2):
 lookup = {'==': operator.eq, '>': operator.gt,
 '<': operator.lt, '!=': operator.ne}
 if str in lookup:
 return lookup[str](value1, value2)
 return False
v1 = 1
v2 = 2
print op("!=", v1, v2)
# True

Answer 2

>>> import operator
>>> ops = {'==': operator.eq,
... '>': operator.gt,
... '<': operator.lt,
... '!=': operator.ne}
>>> ops['=='](1,2)
False
>>> ops['=='](2,2)
True
>>> ops['>'](2,2)
False
>>> ops['>'](3,2)
True
>>> ops['!='](3,2)
True

Answer 3

I think you need to explicitly associate your operators with python's:

import operator as op
oper = '==' ## or '<', etc...
value1 = 1
value2 = 2
opdict = {'<': op.lt, '>': op.gt,
 '<=': op.le, '>=': op.ge,
 '==': op.eq, '!=': op.ne}
if opdict[oper](value1, value2):
 print true

Answer 4

if eval(repr(value1) + operator + repr(value2)):
 print True

or more simply

print eval(repr(value1) + operator + repr(value2))

Just be careful, eval gets a bad reputation =P (seriously tho, the solution with the operator module is probably a better choice)