time库基本使用

概述：time库是python中处理时间的标准库

import time

time.<b>()

包括3类函数：

常用

时间获取：time.time() 时间戳，浮点数（秒）   time.ctime()字符串   time.gmtime()时间元组

时间格式化：time.strftime()时间元组-->字符串   time.strptime()字符串-->时间元组

程序计时：time.sleep()   time.perf_counter

--------------------时间获取

>>> time.time()  # 获取系统当前时间戳，浮点数
1543109157.805488

>>> time.gmtime()  # 获取当前时间，返回时间元组（格林威治时间）
time.struct_time(tm_year=2018, tm_mon=11, tm_mday=25, tm_hour=1, tm_min=45, tm_sec=7, tm_wday=6, tm_yday=329, tm_isdst=0)

gmtime([seconds]) -> (tm_year, tm_mon, tm_mday, tm_hour, tm_min,tm_sec, tm_wday, tm_yday, tm_isdst)

>>> time.localtime()  # 获取当前时间，返回时间元组（本地时间）
time.struct_time(tm_year=2018, tm_mon=11, tm_mday=25, tm_hour=9, tm_min=39, tm_sec=4, tm_wday=6, tm_yday=329, tm_isdst=0)

localtime([seconds]) -> (tm_year,tm_mon,tm_mday,tm_hour,tm_min,
tm_sec,tm_wday,tm_yday,tm_isdst)

>>> time.ctime()  # 获取当前时间以易读方式表示，返回字符串
'Sun Nov 25 09:27:39 2018'

ctime(seconds) -> string

Convert a time in seconds since the Epoch to a string in local time.
This is equivalent to asctime(localtime(seconds)). When the time tuple is
not present, current time as returned by localtime() is used.

time.mktime()  # 把时间元组，转换为秒

mktime(tuple) -> floating point number

>>> time.mktime(time.strptime('20181125 102030','%Y%m%d %H%M%S'))
1543112430.0

>>> time.asctime()
'Sun Nov 25 09:33:48 2018'

asctime([tuple]) -> string

----------------时间格式化

strftime(tpl, ts) # tpl是格式化模板字符串，用来定义输出效果 。ts是时间元组

strftime(format[, tuple]) -> string
>>> time.strftime('%Y-%m-%d %H:%M:%S')
'2018-11-25 09:51:44'

Commonly used format codes:
%Y Year with century as a decimal number.
%m Month as a decimal number [01,12].
%d Day of the month as a decimal number [01,31].
%H Hour (24-hour clock) as a decimal number [00,23].
%M Minute as a decimal number [00,59].
%S Second as a decimal number [00,61].
%z Time zone offset from UTC.
%a Locale's abbreviated weekday name.
%A Locale's full weekday name.
%b Locale's abbreviated month name.
%B Locale's full month name.
%c Locale's appropriate date and time representation.
%I Hour (12-hour clock) as a decimal number [01,12].
%p Locale's equivalent of either AM or PM.

time.strptime(str,tmp)  # 把字符串格式的时间，转换为时间元组

str是字符串形式的时间值 tpl是格式化模板字符串，用来定义输入效果

>>> time.strptime('20181125','%Y%m%d')
time.struct_time(tm_year=2018, tm_mon=11, tm_mday=25, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=6, tm_yday=329, tm_isdst=-1)

-----------------------程序计时

测量时间 time.perf_counter()

返回一个CPU级别的精确时间计数值，单位为秒 由于这个计数值起点不确定，连续调用差值才有意义

>>> start = time.perf_counter()
>>> end = time.perf_counter()
>>> end - start
9.91788138099946

产生时间 time.sleep()

>>> time.sleep(2)
>>>