常用问题库（2）

知识点一： datetime模块（时间）

日期与时间

import os
import datetime
import time

print('-----------日期时间 基本对象----------')
print(datetime.time(15,45,21,100))  #时间
print(datetime.date(2018,3,17)) #日期
print(datetime.datetime(2018,3,17,15,45,21,10001)) #时间+日期

dl=datetime.datetime.now()  #打印出当前时间
print(dl)
du=datetime.datetime.utcnow() #打印出UTC时间
print(du)

print('-------时间戳转换成日期-----------')
ds=os.path.getctime('test.py')
print(datetime.datetime.fromtimestamp(ds))
print('-------日期转换成时间戳-----------')
print(time.mktime(dl.timetuple()))

print('----专门表示时间差的类型------')
da=datetime.timedelta(hours=2,minutes=30)
print(datetime.datetime(2018,2,28,23)+da)

print('-------时间转换成字符串---------')  #实例方法调用
dt=datetime.datetime(2018,3,17,15,45,21,10001)
s=dt.strftime('%m/%d/%y %I:%M:%S %p')   #月/日/年  12小时进制
print(type(s),s)
print('-------字符串转换成时间---------')  #类方法调用
sss=datetime.datetime.strptime(s,'%m/%d/%y %I:%M:%S %p')
print(sss)

#想要表示市区，得有一个时区对象
tz_china=datetime.timezone(offset=datetime.timedelta(hours=8),name='Asia/Beijing ')
tz_us=datetime.timezone(offset=datetime.timedelta(hours=-8),name='Asia/Los Angles ')
dt =datetime.datetime(2018,3,17,17,16,tzinfo=tz_china)  #这个时间带了时区信息

#现在我dt时区的，想要直接转换成美国时区
us_dt=dt.astimezone(tz_us)
print(repr(us_dt),us_dt) 

知识点二： base64 模块（Web编码）

base64模块接口

base64编码，接收一个2二进制的数据，然后把它转换成文本，可以转换回来

标准编码： base64.standard_b64encode(s)

标准解码： base64.standard_b64decode(s)

安全编码： base64.urlsafe_b64encode(s)

标准编码： base64.urlsafe_b64encode(s)

实例：

ttt.py内容：

import base64
with open('aaa.png','rb') as f:
    print(base64.standard_b64encode(f.read()))

#base64是将2进制编码成文本
# 如果是decode，是吧编码成的文本，变成原来的二进制文件
# 网站有两种方法，一种先打开网址，在加载图片，第二种是直接把图片嵌入编码

images.html内容：

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执行结果：