查看eval:

x = 1
print eval('x+1')
->2

Eval和exec是正确的解决方案，使用起来更安全。

正如Python参考手册中所讨论并在本教程中明确解释的那样，eval和exec函数接受两个额外的形参，允许用户指定可用的全局和局部函数和变量。

例如:

public_variable = 10

private_variable = 2

def public_function():
    return "public information"

def private_function():
    return "super sensitive information"

# make a list of safe functions
safe_list = ['public_variable', 'public_function']
safe_dict = dict([ (k, locals().get(k, None)) for k in safe_list ])
# add any needed builtins back in
safe_dict['len'] = len

>>> eval("public_variable+2", {"__builtins__" : None }, safe_dict)
12

>>> eval("private_variable+2", {"__builtins__" : None }, safe_dict)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1, in <module>
NameError: name 'private_variable' is not defined

>>> exec("print \"'%s' has %i characters\" % (public_function(), len(public_function()))", {"__builtins__" : None}, safe_dict)
'public information' has 18 characters

>>> exec("print \"'%s' has %i characters\" % (private_function(), len(private_function()))", {"__builtins__" : None}, safe_dict)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1, in <module>
NameError: name 'private_function' is not defined

实际上，您是在定义代码将在其中执行的名称空间。

使用eval。

Eval()只是用于表达式，而Eval ('x+1')可以工作，Eval ('x=1')则不能工作。在这种情况下，最好使用exec，甚至更好:尝试找到一个更好的解决方案:)

你可以使用exec完成代码的执行，就像下面的IDLE会话一样:

>>> kw = {}
>>> exec( "ret = 4" ) in kw
>>> kw['ret']

4

我尝试了很多方法，但唯一有效的方法是:

temp_dict = {}
exec("temp_dict['val'] = 10") 
print(temp_dict['val'])

输出:

10