No matter which programming language, time is certainly a very important part. Today, let's see how Python handles time and python timing tasks.

Note: This article talks about the implementation of Python 3, which is slightly different in Python 2.

1. Calculate the dates of tomorrow and yesterday

#! /usr/bin/env python
#coding=utf-8
# Get today, yesterday and tomorrow's dates
# Introducing datetime module
import datetime 
#Calculate today's time
today = datetime.date.today()
#Count yesterday's time 
yesterday = today - datetime.timedelta(days = 1)
#Calculate tomorrow's time
tomorrow = today + datetime.timedelta(days = 1) 
#Print these three times
print(yesterday, today, tomorrow)

2. Calculate the last time

Method 1:

#! /usr/bin/env python
#coding=utf-8
# Calculate last time
#Introducing two modules of datetime and calendar
import datetime,calendar
  
last_friday = datetime.date.today() 
oneday = datetime.timedelta(days = 1) 
    
while last_friday.weekday() != calendar.FRIDAY: 
    last_friday -= oneday 
    
print(last_friday.strftime('%A, %d-%b-%Y'))

Method 2: find the last Friday with the help of modular operation

#! /usr/bin/env python
#coding=utf-8
# With the help of modular operation, the number of days to be subtracted can be calculated once, and the last Friday can be calculated.
#It also introduces two modules, datetime and calendar.
import datetime 
import calendar 
    
today = datetime.date.today() 
target_day = calendar.FRIDAY 
this_day = today.weekday() 
delta_to_target = (this_day - target_day) % 7
last_friday = today - datetime.timedelta(days = delta_to_target) 
    
print(last_friday.strftime("%d-%b-%Y"))

3. Calculate the total playing time of songs

#! /usr/bin/env python
#coding=utf-8
# Get the sum of playing time of all songs in a list 
import datetime 
    
def total_timer(times): 
    td = datetime.timedelta(0) 
    duration = sum([datetime.timedelta(minutes = m, seconds = s) for m, s in times], td) 
    return duration 
    
times1 = [(2, 36), 
          (3, 35), 
          (3, 45), 
          ] 
times2 = [(3, 0), 
          (5, 13), 
          (4, 12), 
          (1, 10), 
          ] 
    
assert total_timer(times1) == datetime.timedelta(0, 596) 
assert total_timer(times2) == datetime.timedelta(0, 815) 
    
print("Tests passed.\n"
      "First test total: %s\n"
      "Second test total: %s" % (total_timer(times1), total_timer(times2)))
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4. Execute a command repeatedly

#! /usr/bin/env python
#coding=utf-8
# Execute a command at the required interval 
    
import time, os 
    
def re_exe(cmd, inc = 60): 
    while True: 
        os.system(cmd); 
        time.sleep(inc) 
    
re_exe("echo %time%", 5)

5. Scheduled tasks

#! /usr/bin/env python
#coding=utf-8
#Three modules need to be introduced here
import time, os, sched 
    
# The first parameter determines the time of the task, and returns the number of seconds from a specific time to the present. 
# The second parameter measures time in a human way. 
schedule = sched.scheduler(time.time, time.sleep) 
    
def perform_command(cmd, inc): 
    os.system(cmd) 
        
def timming_exe(cmd, inc = 60): 
    # enter is used to schedule the occurrence time of an event. It starts at the nth second from now on. 
    schedule.enter(inc, 0, perform_command, (cmd, inc)) 
    # Keep running until the scheduled time queue becomes empty 
    schedule.run() 
        
    
print("show time after 10 seconds:") 
timming_exe("echo %time%", 10)

6. Using sched to implement periodic call

#! /usr/bin/env python
#coding=utf-8
import time, os, sched 
    
# The first parameter determines the time of the task, and returns the number of seconds from a specific time to the present. 
# The second parameter measures time in a human way. 
schedule = sched.scheduler(time.time, time.sleep) 
    
def perform_command(cmd, inc): 
    # Schedule yourself to run again after inc seconds, i.e. periodic operation 
    schedule.enter(inc, 0, perform_command, (cmd, inc)) 
    os.system(cmd) 
        
def timming_exe(cmd, inc = 60): 
    # enter is used to schedule the occurrence time of an event. It starts at the nth second from now on. 
    schedule.enter(inc, 0, perform_command, (cmd, inc)) 
    # Keep running until the scheduled time queue becomes empty 
    schedule.run() 
        
    
print("show time after 10 seconds:") 
timming_exe("echo %time%", 10)