推荐学习书目
› Learn Python the Hard Way
Python Sites
› PyPI - Python Package Index
› http://diveintopython.org/toc/index.html
› Pocoo
值得关注的项目
› PyPy
› Celery
› Jinja2
› Read the Docs
› gevent
› pyenv
› virtualenv
› Stackless Python
› Beautiful Soup
› 结巴中文分词
› Green Unicorn
› Sentry
› Shovel
› Pyflakes
› pytest
Python 编程
› pep8 Checker
Styles
› PEP 8
› Google Python Style Guide
› Code Style from The Hitchhiker's Guide
Error - Default argument is mutable
jacklong · jack-long · 2015-03-08 21:54:55 +08:00 · 2915 次点击这是一个创建于 3543 天前的主题，其中的信息可能已经有所发展或是发生改变。
import doctest
def foo(bar=[]):
"""Error: Default argument is mutable.
Default argument values are evaluated only once at function definition time,
which means that modifying the default value of the argument will affect
all subsequent calls of the function.
>>> foo()
['baz']
>>> foo()
['baz', 'baz']
>>> foo()
['baz', 'baz', 'baz']
"""
bar.append("baz")
print bar
doctest.testmod()
 |
1
jacklong OP 代码粘贴进来空格没了，如何缩进？
|
 |
3
dddd 2015-03-08 23:23:26 +08:00
默认参数值是可变对象
可以这样: def foo(bar=None): if bar is None: bar = [] 看这里…… http://effbot.org/zone/default-values.htm |
 |
4
dant 2015-03-08 23:29:25 +08:00 via iPhone
默认参数指向的对象在定义函数的时候就创建了
|
Select Language