Running exec inside function

问题

How can you use the python exec keyword inside functions?

回答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, Python 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.

回答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

回答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

来源：https://stackoverflow.com/questions/2626582/running-exec-inside-function