Python 用datetime模块时间计算精确的天数差

from datetime import datetime
local_time = datetime.now() #获取系统时间 local_time = datetime.datetime.now()
print type(local_time),"local_time= ",local_time
# 字符串转日期
data_time = datetime.strptime('2019-03-20 15:25:30', '%Y-%m-%d %H:%M:%S')
print type(data_time), data_time
Expenses_days = local_time–data_time
print Expenses_days

Python 2.7.14 (v2.7.14:84471935ed, Sep 16 2017, 20:19:30) [MSC v.1500 32 bit (Intel)] on win32
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>>> from datetime import datetime
>>> local_time = datetime.now() #获取系统时间 local_time = datetime.datetime.now()
>>> print type(local_time),"local_time= ",local_time
 local_time=  2019-03-26 22:23:20.742000
>>> # 字符串转日期
... data_time = datetime.strptime('2019-03-20 15:25:30', '%Y-%m-%d %H:%M:%S')
>>> print type(data_time), data_time
 2019-03-20 15:25:30
>>> Expenses_days = local_time-data_time
>>> print Expenses_days
6 days, 6:57:50.742000
>>> print Expenses_days.days
6
>>> print Expenses_days.seconds
25070
>>> print Expenses_days.microseconds
742000
>>> print Expenses_days.days+ Expenses_days.seconds/(24.0*60.0*60.0)
6.29016203704

print Expenses_days 显示  6 days, 6:57:50.742000

print Expenses_days.days  显示  6 天

print Expenses_days.seconds 显示  25070 秒 （25070/(60*60)） = 6.93小时，即6:57:50

print Expenses_days.microseconds 显示 742000 微妙

print Expenses_days.days+ Expenses_days.seconds/(24.0*60.0*60.0)  显示  6.29016203704天

所以当要计算2个精确的天数时间差的时候，需要用.days先算出整天，后用.seconds 算出秒数，再除以24*60*60（一天24小时，一小时60分，一分60秒），2者相加为精确的天数时间差。