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Initial flask and simple application
2022-07-25 14:07:00 【Ride Hago to travel】
Yes , You're not mistaken , The above figure represents Flask. that Flask Why are the gods ？
Flask It's a use Python Written lightweight Web Application framework . Its WSGI The tool box uses Werkzeug , The template engine uses Jinja2 .Flask Use BSD to grant authorization .
Compared with similar frameworks ,Flask The frame looks more flexible , Light , Safe and easy to use ！
One , Configure environment variables before starting
Windows Users can directly access the dos Window or pycharm Below Terminal Enter the following command ：
pip install flask
Two , An example shows Flask ‘ light ’ Where ？
notes ： It is suggested to build a new python project
from flask import Flask
app = Flask(__name__) # Create a Flask object
@app.route('/study') # Use route() Decorator to tell Flask Trigger function URL
def study():
return "<h1>Hello Word!</h1>"
app.run() # Start the service
pycharm Right click directly in run Can run 
notes ： It can be seen from the running results in the above figure Flask The default port is 5000, and Django The default port is 8000, Tornado The default port is 8888;
Just six lines of code , You can run , Dare you say it doesn't ‘ light ’？
3、 ... and , Simply start a user management system
Actually , If you are right Django I know something about the framework , To learn Flask Will appear very calm .
1, Realize simple user login
from flask import Flask, request, render_template
app = Flask(__name__) # Create a Flask object
@app.route('/login', methods=['GET', 'POST', ]) # mothods=['GET', 'POST', ] Indicates that you can send GET request , It can also be sent POST request
def login():
if request.method == "GET": # If it's sending GET request
return render_template('login.html') # Use render_template() Method to render templates , amount to Django Medium render()
else:
user = request.form.get('username') # request.form.get() Said by post Method to get the value
pwd = request.form.get('password')
if user == 'hpl' and pwd == '123456':
return "<h1> Congratulations on your successful login ！</h1>"
else:
return render_template('login.html', error=' Wrong user name or password ！')
app.run(debug=True) # Start the service debug=True Said to start debug mode
Create a file named... In the root directory templates Folder , Users place templates ( and Django It's similar to ); And create a login.html file , The contents are as follows ：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title> Welcome to the landing page </title>
</head>
<body>
<h1> Sign in </h1>
<form action="" method="post">
<p>
<label for=""> user name ：</label>
<input type="text" name="username">
</p>
<p>
<label for=""> password ：</label>
<input type="password" name="password">
<span style="color:red;">{
{ error }}</span>
</p>
<button> Submit </button>
</form>
</body>
</html>
run once , The result is ：
When the user name or password is wrong ：
When the user name and password are correct ：
2, Put the user's login information into session in
from flask import Flask, request, render_template, session
app = Flask(__name__) # Create a Flask object
app.secret_key = 'jkdfgd' # Equivalent to adding salt ( I'm not sure what's in it )
@app.route('/login', methods=['GET', 'POST', ]) # mothods=['GET', 'POST', ] Indicates that you can send GET request , It can also be sent POST request
def login():
if request.method == "GET": # If it's sending GET request
return render_template('login.html') # Use render_template() Method to render templates , amount to Django Medium render()
else:
user = request.form.get('username') # request.form.get() Said by post Method to get the value
pwd = request.form.get('password')
# Put user information in session
session['user_information'] = user
if user == 'hpl' and pwd == '123456':
return "<h1> Congratulations on your successful login ！</h1>"
else:
return render_template('login.html', error=' Wrong user name or password ！')
app.run(debug=True) # Start the service debug=True Said to start debug mode
After logging in again , Here's the picture 
3, Display basic user information and detailed information
from flask import Flask, request, render_template, session, redirect
USER_DICT = {
'1': {
'name': ' Bald head strength ', 'age': 30, 'sex': ' male ', 'address': ' Tuanjietun '},
'2': {
'name': ' Big marmoset ', 'age': 25, 'sex': ' male ', 'address': ' Unknown '},
'3': {
'name': ' Er Gouzi ', 'age': 26, 'sex': ' male ', 'address': ' Unknown '},
'4': {
'name': ' Boss Li ', 'age': 42, 'sex': ' male ', 'address': ' Metropolis '},
'5': {
'name': ' Cui Hua ', 'age': 18, 'sex': ' Woman ', 'address': ' The forest '},
}
app = Flask(__name__) # Create a Flask object
app.secret_key = 'jkdfgd' # Equivalent to adding salt ( I'm not sure what's in it )
@app.route('/login', methods=['GET', 'POST', ]) # mothods=['GET', 'POST', ] Indicates that you can send GET request , It can also be sent POST request
def login():
if request.method == "GET": # If it's sending GET request
return render_template('login.html') # Use render_template() Method to render templates , amount to Django Medium render()
else:
user = request.form.get('username') # request.form.get() Said by post Method to get the value
pwd = request.form.get('password')
# Put user information in session
session['user_information'] = user
if user == 'hpl' and pwd == '123456':
return redirect('/index') # Redirect ( and Django It's similar to )
else:
return render_template('login.html', error=' Wrong user name or password ！')
@app.route('/index', methods=['GET', ], endpoint='index') # Same as Django Medium name, For reverse parsing
def index():
user_info = session.get('user_information')
if not user_info:
return redirect('/login')
return render_template('index.html', user_dict=USER_DICT)
@app.route('/detail', methods=['GET', ], endpoint='detail')
def detail():
user_info = session.get('user_information')
if not user_info:
return redirect('/login')
user_id = request.args.get('user_id')
info = USER_DICT.get(user_id)
return render_template('detail.html', info=info)
app.run(debug=True) # Start the service debug=True Said to start debug mode
stay templates Create under folder index.html Document and detail.html file
index.html in
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title> User information </title>
</head>
<body>
<h2> User information </h2>
<table border="1px" cellspacing="0" cellpadding="5px">
<thead>
<tr>
<th> full name </th>
<th> operation </th>
</tr>
</thead>
<tbody>
{
% for k,v in user_dict.items() %}
<tr>
<td>{
{
v.name }}</td>
<td><a href="/detail?user_id={
{ k }}"> Check the details </a></td>
</tr>
{
% endfor %}
</tbody>
</table>
</body>
</html>
detail.html in
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title> Information details display page </title>
</head>
<body>
<h1> Details </h1>
<table border="1px" cellpadding="5px" cellspacing="0">
<thead>
<tr>
<th> full name </th>
<th> Age </th>
<th> Gender </th>
<th> address </th>
</tr>
</thead>
<tbody>
<tr>
<td>{
{
info.name }}</td>
<td>{
{
info.age }}</td>
<td>{
{
info.sex }}</td>
<td>{
{
info.address }}</td>
</tr>
</tbody>
</table>
</body>
</html>
The result is 
4, Log out
from flask import Flask, request, render_template, session, redirect
USER_DICT = {
'1': {
'name': ' Bald head strength ', 'age': 30, 'sex': ' male ', 'address': ' Tuanjietun '},
'2': {
'name': ' Big marmoset ', 'age': 25, 'sex': ' male ', 'address': ' Unknown '},
'3': {
'name': ' Er Gouzi ', 'age': 26, 'sex': ' male ', 'address': ' Unknown '},
'4': {
'name': ' Boss Li ', 'age': 42, 'sex': ' male ', 'address': ' Metropolis '},
'5': {
'name': ' Cui Hua ', 'age': 18, 'sex': ' Woman ', 'address': ' The forest '},
}
app = Flask(__name__) # Create a Flask object
app.secret_key = 'jkdfgd' # Equivalent to adding salt ( I'm not sure what's in it )
@app.route('/login', methods=['GET', 'POST', ]) # mothods=['GET', 'POST', ] Indicates that you can send GET request , It can also be sent POST request
def login():
if request.method == "GET": # If it's sending GET request
return render_template('login.html') # Use render_template() Method to render templates , amount to Django Medium render()
else:
user = request.form.get('username') # request.form.get() Said by post Method to get the value
pwd = request.form.get('password')
# Put user information in session
session['user_information'] = user
if user == 'hpl' and pwd == '123456':
return redirect('/index')
else:
return render_template('login.html', error=' Wrong user name or password ！')
@app.route('/index', methods=['GET', ], endpoint='index')
def index():
user_info = session.get('user_information')
if not user_info:
return redirect('/login')
return render_template('index.html', user_dict=USER_DICT)
@app.route('/detail', methods=['GET', ], endpoint='detail')
def detail():
user_info = session.get('user_information')
if not user_info:
return redirect('/login')
user_id = request.args.get('user_id')
info = USER_DICT.get(user_id)
return render_template('detail.html', info=info)
@app.route('/logout', methods=['GET', ])
def logout():
del session['user_information'] # Delete session You can log out
return redirect('/login')
app.run(debug=True) # Start the service debug=True Said to start debug mode
More details , see Flask Developing documents ：https://dormousehole.readthedocs.io/en/latest/
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