Running exec inside function

Question

如何在函数中使用 python exec 关键字？

Answer 1

It's going to damage your function's performance, as well as its maintainability, but if you really want to make your own code so much worse, Python2 (this will not work in Python3, there you need to use the second alternative) gives you "enough rope to shoot yourself in the foot" (;-):

>>> def horror():
...   exec "x=23"
...   return x
... 
>>> print horror()
23

A tad less horrible, of course, would be to exec in a specific dict:

>>> def better():
...   d = {}
...   exec "x=23" in d
...   return d['x']
... 
>>> print better()
23

This at least avoids the namespace-pollution of the first approach.

Answer 2

Alex's answer works slightly differently in Python 3.

Since exec() is a function in Python 3, use the following pattern-

def better():
    d = {}
    exec("x=23", d)
    return d['x']

print better()
23

See this question for more details- Behavior of exec function in Python 2 and Python 3

Answer 3

Yes.

class A:
    def __init__(self):
        self.a1 = ''
        self.a2 = ''

def populate():
    att1 = raw_input("enter a1: ")
    att2 = raw_input("enter a2: ")
    my_object = A()
    eval("my_obj.a1 = att1")
    eval("my_obj.a2 = att2")
    if eval("my_obj.a2") == 2:
    print "Hooray! the value of a2 in my_obj is 2"

Hope this helps