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1. Send mail

2. Operation database: MySQLdb

3. Web crawler: requests

4. Operation execl: pandas

5. Operating system interface

6. Data analysis: numpy

7. Data drawing analysis: Matplotlib

8. String regular matching

9. Game development: pygame

10. Data compression

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1. Send mail

There are several modules for accessing the Internet and handling network communication protocols. The simplest two are urllib.request for processing data received from urls and SMTP lib for sending e-mail:

import smtplib
smtpObj = smtplib.SMTP( [host [, port [, local_hostname]]] )

Parameter Description:

  • host: SMTP server host. You can specify the ip address or domain name of the host, such as runoob.com. This is an optional parameter.
  • Port: if you provide the host parameter, you need to specify the port number used by the SMTP service. Generally, the SMTP port number is 25.
  • local_hostname: if SMTP is on your local machine, you only need to specify the server address as localhost.

The Python SMTP object uses the sendmail method to send mail. The syntax is as follows:

SMTP.sendmail(from_addr, to_addrs, msg[, mail_options, rcpt_options])

Parameter Description:

  • from_addr: mail sender address.
  • to_addrs: string list, email address.
  • msg: send message


# -*- coding: UTF-8 -*-
import smtplib
from email.mime.text import MIMEText
from email.header import Header
sender = 'from@runoob.com'
# Official account: information technology think tank
receivers = ['429240967@qq.com']  # To receive mail, you can set it as your QQ mailbox or other mailboxes
# Three parameters: the first is the text content, the second is to set the text format, and the third is utf-8 to set the code
message = MIMEText('Python Mail sending test...', 'plain', 'utf-8')
message['From'] = Header("Tomato God", 'utf-8')   # sender 
message['To'] =  Header("test", 'utf-8')        # recipient
subject = 'Python SMTP Mail test'
message['Subject'] = Header(subject, 'utf-8')
    smtpObj = smtplib.SMTP('localhost')
    smtpObj.sendmail(sender, receivers, message.as_string())
    print "Mail sent successfully"
except smtplib.SMTPException:
    print "Error: Unable to send message"

2. Operation database: MySQLdb

To install MySQL dB, please visit http://sourceforge.net/projects/mysql-python  

Operate mysql to query data

import MySQLdb
# Connect to database
conn = MySQLdb.connect(host='localhost',user='root',passwd='xxxx',db='test1')

# Get cursor object for operation
cursor = conn.cursor()

# More information: https://t.1yb.co/zHJo
sql = "select * from world where someone like 'you' "

# Execute sql

3. Web crawler: requests

Requests allows you to send natural HTTP/1.1 requests without manual labor. You don't need to add query strings to the URL manually, and you don't need to encode the POST data. Keep alive and HTTP connection pooling are 100% automated.

A simple crawler example:

#Official account: information technology think tank
import requests
heads = {}
heads['User-Agent'] = 'Mozilla/5.0 ' \
                          '(Macintosh; U; Intel Mac OS X 10_6_8; en-us) AppleWebKit/534.50 ' \
                          '(KHTML, like Gecko) Version/5.1 Safari/534.50'

response = requests.get('http://www.baidu.com',headers=headers)

4. Operation execl: pandas

# -*- coding: utf-8 -*-
import xlrdimport xlwt
from datetime import date,datetime

def read_excel():
    # Open file
    workbook = xlrd.open_workbook(r'F:\demo.xlsx')
    # Get all sheet s
    print workbook.sheet_names() # [u'sheet1', u'sheet2']
    sheet2_name = workbook.sheet_names()[1]

    # Get sheet content according to sheet index or name
    sheet2 = workbook.sheet_by_index(1) # sheet index starts from 0
    sheet2 = workbook.sheet_by_name('sheet2')

    # Name of sheet, number of rows and columns
    print sheet2.name,sheet2.nrows,sheet2.ncols

    # Gets the value of the entire row and column (array)
    rows = sheet2.row_values(3) # Get the fourth line
    cols = sheet2.col_values(2) # Get the contents of the third column
    print rows
    print cols

    # Get cell content
    print sheet2.cell(1,0).value.encode('utf-8')
    print sheet2.cell_value(1,0).encode('utf-8')
    print sheet2.row(1)[0].value.encode('utf-8')
    # Gets the data type of the cell content
    print sheet2.cell(1,0).ctype

if __name__ == '__main__':

5. Operating system interface

The os module provides many functions associated with the operating system.

>>> import os
>>> os.getcwd()      # Returns the current working directory
>>> os.chdir('/server/accesslogs')   # Modify the current working directory
>>> os.system('mkdir today')   # Execute the system command mkdir 

It is recommended to use the "import os" style instead of "from os import *. This ensures that os.open(), which varies with the operating system, does not override the built-in function open().

os common commands

Serial numbermethodfunction
1os.access(path, mode)  Check permission mode
2os.chdir(path)   Change current working directory
3os.chflags(path, flags)  Set the marker of the path as a numeric marker.
4os.chmod(path, mode)    change permission
5os.chown(path, uid, gid)  Change file owner
6os.chroot(path)   Change the root directory of the current process
7os.close(fd)    Close file descriptor fd
8os.closerange(fd_low, fd_high)    Close all file descriptors from fd_low (inclusive) to fd_high (not included), errors are ignored
9os.dup(fd)    Copy file descriptor fd
10os.dup2(fd, fd2)    

Copy one file descriptor FD to another fd2

6. Data analysis: numpy

NumPy contains a large number of functions of various mathematical operations, including trigonometric functions, functions of arithmetic operations, complex number processing functions, etc.

NumPy provides a variety of sorting methods. These sorting functions implement different sorting algorithms. Each sorting algorithm is characterized by execution speed, worst-case performance, required workspace and algorithm stability. The following table shows a comparison of the three sorting algorithms.

trigonometric function

NumPy provides standard trigonometric functions: sin(), cos(), tan().

import numpy as np
a = np.array([0,30,45,60,90])
print ('Sinusoidal values at different angles:')
# Convert to radians by multiplying pi/180  
print (np.sin(a*np.pi/180))
print ('\n')
print ('Cosine value of the angle in the array:')
print (np.cos(a*np.pi/180))
print ('\n')
print ('Tangent value of angle in array:')
print (np.tan(a*np.pi/180))

7. Data drawing analysis: Matplotlib

import numpy as np 
from matplotlib import pyplot as plt 
x = np.arange(1,11) 
y =  2  * x +  5 
plt.title("Matplotlib demo") 
plt.xlabel("x axis caption") 
plt.ylabel("y axis caption") 

In the above example, the NP. Orange() function creates a value on the x-axis. The corresponding value on the y-axis is stored in another array object y. These values are plotted using the plot() function of the pyplot sub module of the matplotlib package.

The graph is displayed by the show() function.

8. String regular matching

The re module provides regular expression tools for advanced string processing. It can be said that regular expressions are necessary for crawlers. For complex matching and processing, regular expressions provide concise and optimized solutions: if only simple functions are required, string methods should be considered first, because they are very simple and easy to read and debug:

>>> 'tea for too'.replace('too', 'two')
'tea for two'

re.match function

re.match attempts to match a pattern from the start of the string. If the start is not matched successfully, match() returns none.

Function syntax:

re.match(pattern, string, flags=0)

Function parameter description:

patternMatching regular expressions
stringString to match.
flagsFlag bit, used to control the matching method of regular expressions, such as case sensitive, multi line matching, etc.

Matching succeeded. The re.match method returns a matching object, otherwise it returns None.

We can use the group(num) or groups() matching object function to get the matching expression.

Matching object methoddescribe
group(num=0)group() can enter multiple group numbers at a time, in which case it will return a tuple containing the values corresponding to those groups.
groups()Returns a tuple containing all group strings, from 1 to the contained group number.

9. Game development: pygame

  • Pygame is a set of cross platform Python modules for creating video games.
  • It consists of a computer graphics and sound library designed for use with the Python programming language.
  • Pygame was formally written by Pete Shinners to replace PySDL.
  • Pygame is suitable for creating client applications that can be wrapped in separate executables.
import pygame

screen = pygame.display.set_mode((400, 500))
done = False

while not done:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True

10. Data compression

The following modules directly support common data packaging and compression formats: zlib, gzip, bz2, zipfile, and tarfile.

>>> import zlib
>>> s = b'witch which has which witches wrist watch'
>>> len(s)
>>> t = zlib.compress(s)
>>> len(t)
>>> zlib.decompress(t)
b'witch which has which witches wrist watch'
>>> zlib.crc32(s)

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[title]: Python 3.x basic tutorial

[how to get]: leave a comment in the comment area to like the collection. Draw 2 people from the comment area through the python random function. I will talk privately about the winners, provide address information, and publicize the express record in the next issue.

[content introduction]

The Python 3.x basic tutorial aims to help readers master the basic knowledge of Python language, how to use Python language to realize programming, understand its development skills, and be familiar with the development process and problem solutions through practical cases.
The book is divided into 13 chapters, which are roughly divided into four parts: Chapter 1 ~ 4 introduce Python introduction and environment construction, python foundation and object-oriented programming knowledge; Chapter 5 ~ 7 introduces the knowledge of reading and writing files, built-in battery module and system programming; Chapter 8 ~ 11 introduces network programming, sending and receiving e-mail, graphical user interface and Web development; Chapters 12 and 13 integrate the knowledge points of the book through the explanation of two comprehensive cases, so as to deepen the readers' understanding of the knowledge.

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Posted by rarebit on Sat, 18 Sep 2021 07:37:22 -0700