python 对日期的处理

转换关系图

struct time

# struct time
time_array = time.localtime()
print(time_array)
print(time_array.tm_year)  # 其他属性类似

# time.struct_time(tm_year=2020, tm_mon=2, tm_mday=26, tm_hour=23, tm_min=59, tm_sec=32, tm_wday=2, tm_yday=57, tm_isdst=0)
# 2020

图中 4 条边的实现方式

从图中可以看出：

1. timestr => timestamp 可以通过 timestr => struct_time => timestamp 来实现。
2. timestamp => timestr 可以通过 timestamp => struct_time => timestr 来实现。

# struct time => timestr
time_str = time.strftime("%Y-%m-%d", time_array)
print(time_str)
time_str = time.strftime("%Y-%m-%d %H:%M:%S", time_array)
print(time_str)

# struct time => timestamp
time_array = time.localtime()
timestamp = int(time.mktime(time_array))
print(timestamp)

# timestr => struct time
time_str = "2020-02-26 23:59:32"
time_array = time.strptime(time_str, "%Y-%m-%d %H:%M:%S")
print(time_array)

# timestamp => sturct time
timestamp = 1582732864
time_array = time.localtime(timestamp)
print(time_array)

timestamp = 1582732864
time_array = time.gmtime(timestamp)
print(time_array)

获取 N 天前的日期

# 获取 90 天前的日期
import datetime

today = datetime.date.today()
numday = datetime.timedelta(days=90) 
numday_ago_date = today - numday
print(today)
print(numday_ago_date)