python defined是什么意思"/>
python defined是什么意思
判断变量是否定义
# 如果C有值就取C,否则自定义为8
a = 8 if not c else c
Traceback (most recent call last):
File "", line 1, in
a = 8 if not c else c
NameError: name 'c' is not defined
呵呵,结果,发现c未定义,not defined,不是None
碰到这种问题该怎么解决呢?
目前判断变量有二种方式:
一般方式:try···except
try:
a = 8 if not c else c
except:
a = 8
dir() /local()判断
我们先来看看IDLE 上他们的表现
Python 3.4.3 (default, Oct 14 2015, 20:28:29)
[GCC 4.8.4] on linux
Type "copyright", "credits" or "license()" for more information.
>>> dir()
['__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__']
>>> locals()
{'__doc__&
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python defined是什么意思
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