Question

I need to call a function whose name is available in a string in python
eg:

   [(x, y) for x in [1,2,3] for y in [3,1,4] if x != y]

I need to execute the above statement but the variable count may increase according to user input any idea?

Another Example :

a = "for y in range(2,20):print y"

I need to execute the above string as a python command

Actual Problem is no of loops and variable may increase depends upon the input
somtimes i wnat to iterate over 3 item so 3 loops sometime 4 item then 4 loops
so i figured out this way if i generate string with the variables and if i can execute it problem can be solved

Answer 1

The built-in eval function is what you are looking for:

s = "[(x, y) for x in [1,2,3] for y in [3,1,4] if x != y]"
result = eval(s)

If you want variables, you can use the locals argument:

>>> eval("s.upper()",{'s':'hello'})
'HELLO'

If you want to execute statements instead of evaluating expressions, use exec:

>>> a = "for y in range(2,20):print y"
>>> exec a
2
3
...
19