learning-python/misc/test_exec.py at master · lylang/learning-python

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# -*- coding: utf-8 -*-

# Exec与Eval语句的区别: Exec处理字符串里的代码, 而Eval是处理字符串里面的表达式.

# exec_stmt ::= "exec" or_expr ["in" expression ["," expression]]

# exec的第一个表达式可以是

# 代码字符串

# 文件对象

# 代码对象

# tuple

# test1 如果忽略后面的可选表达式,exec后面代码将在当前域执行

a = 2

exec "a=1"

print(a)

# test2 如果在表达式之后使用in选项指定一个dic，它将作为global和local变量作用域

a = 10

b = 20

g = {'a': 6, 'b': 8}

exec "global a; print a,b" in g

exec "b; print a,b" in g

# test3 如果in后详指定两个表达式，它们将分别用作global和local变量作用域

a = 10

b = 20

c = 20

g = {'a': 6, 'b': 8}

l = {'b': 9, 'c': 10}

exec "global b; print a, b, c" in g, l

# tuple

# exec(expr, globals) #它等效于 exec expr in globals

# exec(expr, globals, locals) #它等效于 exec expr in globals,locals

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