Python模块导入

1、 import

想使用Python源文件，只需在另一个源文件里执行import语句，语法如下：

import numpy
n = numpy.array([[1,2],[3,4]])
n

array([[1, 2],
       [3, 4]])

import matplotlib.pyplot as plt
plt.plot(n)
plt.show()

2、from...import*

这提供了一个简单的方法来导入一个模块中的所有项目。然而这种声明不该被过多地使用。
把一个模块的所有内容全都导入到当前的命名空间也是可行的，只需使用如下声明：

from datetime import *

time

datetime.time

3、 from...import语句：

Python的from语句让你从模块中导入一个指定的部分到当前命名空间中。

dir()函数一个排好序的字符串列表，返回的列表容纳了在一个模块里定义的所有模块，变量和函数。

from datetime import time
dir(time)

['__class__',
 '__delattr__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__gt__',
 '__hash__',
 '__init__',
 '__init_subclass__',
 '__le__',
 '__lt__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 'dst',
 'fold',
 'hour',
 'isoformat',
 'max',
 'microsecond',
 'min',
 'minute',
 'replace',
 'resolution',
 'second',
 'strftime',
 'tzinfo',
 'tzname',
 'utcoffset']

help(time)

Help on class time in module datetime:

class time(builtins.object)
 |  time([hour[, minute[, second[, microsecond[, tzinfo]]]]]) --> a time object
 |  
 |  All arguments are optional. tzinfo may be None, or an instance of
 |  a tzinfo subclass. The remaining arguments may be ints.
 |  
 |  Methods defined here:
 |  
 |  __eq__(self, value, /)
 |      Return self==value.
 |  
 |  __format__(...)
 |      Formats self with strftime.
 |  
 |  __ge__(self, value, /)
 |      Return self>=value.
 |  
 |  __getattribute__(self, name, /)
 |      Return getattr(self, name).
 |  
 |  __gt__(self, value, /)
 |      Return self>value.
 |  
 |  __hash__(self, /)
 |      Return hash(self).
 |  
 |  __le__(self, value, /)
 |      Return self<=value.
 |  
 |  __lt__(self, value, /)
 |      Return self<value.
 |  
 |  __ne__(self, value, /)
 |      Return self!=value.
 |  
 |  __new__(*args, **kwargs) from builtins.type
 |      Create and return a new object.  See help(type) for accurate signature.
 |  
 |  __reduce__(...)
 |      __reduce__() -> (cls, state)
 |  
 |  __reduce_ex__(...)
 |      __reduce_ex__(proto) -> (cls, state)
 |  
 |  __repr__(self, /)
 |      Return repr(self).
 |  
 |  __str__(self, /)
 |      Return str(self).
 |  
 |  dst(...)
 |      Return self.tzinfo.dst(self).
 |  
 |  isoformat(...)
 |      Return string in ISO 8601 format, [HH[:MM[:SS[.mmm[uuu]]]]][+HH:MM].
 |      
 |      timespec specifies what components of the time to include.
 |  
 |  replace(...)
 |      Return time with new specified fields.
 |  
 |  strftime(...)
 |      format -> strftime() style string.
 |  
 |  tzname(...)
 |      Return self.tzinfo.tzname(self).
 |  
 |  utcoffset(...)
 |      Return self.tzinfo.utcoffset(self).
 |  
 |  ----------------------------------------------------------------------
 |  Data descriptors defined here:
 |  
 |  fold
 |  
 |  hour
 |  
 |  microsecond
 |  
 |  minute
 |  
 |  second
 |  
 |  tzinfo
 |  
 |  ----------------------------------------------------------------------
 |  Data and other attributes defined here:
 |  
 |  max = datetime.time(23, 59, 59, 999999)
 |  
 |  min = datetime.time(0, 0)
 |  
 |  resolution = datetime.timedelta(0, 0, 1)

time(23, 59, 59, 999999).microsecond

999999

time?