exec
exec语句用来执行储存在字符串或文件中的Python语句, 我们可以运行一个包含Python语句的字符串
>>> exec "print 'Hello Python'"
Hello Python
但是exec可能会干扰Python语句的命名空间, 从而影响到原来的函数运行
>>> from math import sqrt
>>> exec "sqrt = 1"
>>> sqrt(4)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'int' object is not callable
解决方案:
>>> from math import sqrt
>>> temp = {}
>>> exec "sqrt = 1" in temp
>>> sqrt(4)
2.0
>>> temp['sqrt']
1
eval
>>> eval(raw_input('input two number: '))
input two number: 2+3*5
17