Python 导入所需模块
以下代码按预期工作。但我有两个问题Python 导入所需模块,python,Python,以下代码按预期工作。但我有两个问题 # import datetime # does not work from datetime import datetime row = ('2002-01-02 00:00:00.3453', 'a') x = datetime.strptime(row[0], "%Y-%m-%d %H:%M:%S.%f") 1) 为什么只导入datetime不起作用 2) 如何知道“strTime”方法属于哪个模块 >>> help('modules
# import datetime # does not work
from datetime import datetime
row = ('2002-01-02 00:00:00.3453', 'a')
x = datetime.strptime(row[0], "%Y-%m-%d %H:%M:%S.%f")
1) 为什么只导入datetime不起作用
2) 如何知道“strTime”方法属于哪个模块
>>> help('modules strptime')
不提供我正在寻找的信息
datetime
是一个模块。它还有一个名为datetime的成员,该成员有一个名为strtime1)的方法,工作正常。但是其中的datetime
类是独立的。您需要将其称为datetime.datetime
2) 使用。但是方法属于对象,而不是模块。方法是
datetime.datetime.strtime
,当您执行一个简单的导入datetime
时,您只导入顶级模块,而不是datetime
类
您可以这样进行测试:
>>> import datetime
>>> locals()
{'__builtins__': <module '__builtin__' (built-in)>, '__name__': '__main__', 'dat
etime': <module 'datetime' (built-in)>, '__doc__': None, '__package__': None}
>>> from datetime import datetime
>>> locals()
{'__builtins__': <module '__builtin__' (built-in)>, '__name__': '__main__', 'dat
etime': <type 'datetime.datetime'>, '__doc__': None, '__package__': None}
导入日期时间
>>>本地人()
{uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu
时间“:,”文档“,”无“,”包“,”无“}
>>>从日期时间导入日期时间
>>>本地人()
{uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu
时间“:,”文档“,”无“,”包“,”无“}
您可以看到名称空间中有两个不同的对象
对于第二个问题,Python内置的help()
仅适用于加载的模块和对象。如果您没有导入日期时间,help()
将帮不上忙。因此,最好浏览文档以了解这一点;而在python strtime
上的google通常会让您进入正确的文档页面。您可以:
import datetime
x = datetime.datetime.strptime(row[0], "%Y-%m-%d %H:%M:%S.%f")
或者你会:
from datetime import datetime
x = datetime.strptime(row[0], "%Y-%m-%d %H:%M:%S.%f")
您知道strtime属于什么,因为代码告诉您:它附加到刚刚导入的
datetime
。