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Preface

Hello . Here is Python Reptiles from getting started to giving up series of articles . I am a SunriseCai.

This article is my usual study Python Some knowledge points commonly used in , Don't be Python System learning .

Python Common basic usage

Python Basic data structure

This is simpler , It is recommended to click the link directly to check the usage .

Python Placeholders and format()

Definition ：

Place holder % Example ：

name = input(' Type in your name ：') # SunriseCai
age = input(' Enter your age ：') # 20
weight= input(' Enter your weight ：') # 65.432
print(' Your name is %s, Age is %d, Height is %.2f kg ' % (name, int(age), float(weight)))
# Your name is SunriseCai, Age is 20, The weight is 65.43 kg
# %.2f It means taking 2 Decimal place

format() Format example ：

name = input(' Type in your name ：') # SunriseCai
age = input(' Enter your age ：') # 20
weight = input(' Enter your salary ：') # 65.432
print(' Your name is {}, Age is {}, The weight is {} kg '.format(name, age, weight))
# Your name is SunriseCai, Age is 20, The weight is 65.432 kg

Python Conditional statements

Python Programming if Statement is used to control the execution of a program , The basic form is ：

if Judge the condition 1：
Execute statement A
elif Judge the condition 2:
Execute statement B
else：
Execute statement C

To understand is ： If meet Conditions 1 execute A, dissatisfaction Conditions 1 But satisfied Conditions 2 execute B, If neither of them is satisfied, they will execute C.
Example ：

num = 10
if num > 10: # Judge num
print(' I am bigger than 10')
elif num < 10: # num Less than 10 It outputs
print(' I am smaller than 10')
else: # If the above is not satisfied, output
print(' I am equal to 10')
# Final output I am equal to 10

Python Loop statement

Here's a quote from the rookie tutorial Python Loop statement .

• Python Provides for Circulation and while loop ：

while Loop example ：

• Always print the input string , Until input end Exit loop .

while True:
string = input(' Input string ：')
if string == 'end':
break # Exit loop
print(string)

for Loop example ：

• repeat 100 Print through Hello World.

for i in range(100):
print('Hello World')

Python Of join()、split()、strip()

Example ：

• Python join() ：

string = ['SunriseCai', 'SunriseCai', 'SunriseCai']
print('--'.join(string)) # SunriseCai--SunriseCai--SunriseCai

• Python strip()：

string = '%#SunriseCai%#'
print(string.strip('%#')) # SunriseCai

• Python split()：

string = '%#SunriseCai%#'
print(string.split('%#')) # ['', 'SunriseCai', '']

Python exception handling

Python Commonly used try/except Statement fetch catch exception .
Common use ：

• Normal execution A, If the error is reported, execute B,C No matter whether there is an error or not, it will be executed .

try:
Execute statement A
except Exception as e:
Execute statement B
# raise NameError # once raise perform ,raise None of the following statements will be executed
finally:
Execute statement C

Example ：

try:
print(1 / 0) # 1 Divide 0 Will report a mistake
except Exception as e:
print(e)
finally:
print('SunriseCai')
# division by zero
# SunriseCai

Common modules

The method called by the module ：

time modular

• Sleep 10 second ：

import time
time.sleep(10) # here Python The program will sleep 10 second

• Get the current timestamp , namely 1970.01.01 How many seconds have passed by now ：

import time
print(time.time()) # 1578838874.4708762

• Get the current date ：

import time
stamp = time.time()
print(time.strftime('%Y-%m-%d', time.localtime(stamp))) # 2020-01-12

• Get the current date Minutes and seconds ：

import time
stamp = time.time()
print(time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(stamp))) # 2020-01-12 22:20:20

os modular

• os Module provides a very rich way to handle files and directories . The common methods are shown in the following table ：

It's usually os These two methods of os.path.exists(path) and os.makedirs(path) Most used . Judge whether the document exists or not , Then judge if the next file needs to be created .

json modular

• json The module mainly uses two methods ：

above , Is in Python Reptiles Very few knowledge points commonly used in .
There are many knowledge points and modules that will be used , Here, just remember some of the most used .

Finally, I will summarize the content of this chapter ：

1. It introduces Python Basic data structure
2. It introduces Place holder And format()
3. It introduces Conditional statements And Loop statement 、 exception handling etc.
4. It introduces join、split、strip Handling sequence and string usage
5. Finally, it introduces time、os、json Basic usage of module

• Thank you for your patience in watching , Focus , Neverlost .
• For the convenience of chicken pecking each other , Welcome to join QQ Group organization ：648696280( There is no learning material in it , Just for questions )

Next article , be known as 《Python Reptiles from getting started to giving up 03 | Python Advanced usage in reptile 》.