Flask application (form processing) in python

The content of this article is about flask application (form processing) in Python. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

1. Why use Flask-WTF?

The request object exposes all request information sent by the client. In particular, request.form has access to form data submitted by POST requests.
Although the support provided by Flask's request object is sufficient to handle web forms, there are still many tasks that can become monotonous and repetitive.
Form HTML code generation and validation of submitted form data are two good examples.

Advantages:

Flask-WTF extension makes processing web forms a more pleasant experience. This extension is a Flask integration that wraps the framework-independent WTForms package.

2. What is form processing?

In a web page, some forms always have to appear in order to interact with users.
flask designed the WTForm form library to make it easier for flask to manage and operate form data.

The most important concepts in WTForm are as follows:

1). Form class, developer-defined forms must inherit from the Form class or its subclasses.
The main function of the Form class is to provide quick access to data in the form through the Field class it contains.

2). Various Field classes, namely fields. Generally speaking, each Field class corresponds to an input HTML tag.
For example, some of the Field classes that come with WTForm, such as BooleanField, correspond to ,
SubmitField corresponds to , etc.

3). Validator class. This class is used to verify the validity of data entered by the user.
For example, the Length validator can be used to verify the length of input data,
FileAllowed verifies the type of uploaded files, etc.

In addition, in order to prevent csfr (cross-site request forgery) attacks, flask requires the app to set secret_key by default before using flask-wtf. The simplest way to configure it is through app.config['SECRET_KEY'] = 'xxxx'.

3. Common Field classes

PasswordField Password field, automatically converts input into small black dots

DateField Text field, the format requirement is datetime .date is the same

IntergerField Text field, the format requirement is an integer

DecimalField Text field, the format requirement is the same as decimal.Decimal

FloatField Text field, the value is a floating point number

BooleanField 　 Check box, the value is True or False

RadioField 　 A set of radio button boxes

SelectField 　 Drop-down list, it should be noted that the choices parameter determines the drop-down option, but it is different from Like the tag in HTML, it is a list of tuples. The first item of each tuple can be considered to be the real value of the option, and the second item is the alias.

MultipleSelectField A drop-down list with multiple optional values

Validator verification function

Validator is a verification function that binds a field to a verification function Afterwards, flask will verify the data before receiving the data in the form. If the verification is successful, the data will be received. The verification function Validator is as follows. Specific validators may require different parameters. Here are only some commonly used ones. For more detailed usage, please refer to the source code of the wtforms/validators.py file and see what parameters each validator class requires:

*Basically every validator has a message parameter, which indicates what information is displayed when the input data does not meet the requirements of the validator.

Email Verify the validity of the email address, the required regular pattern is ^. @(¹² )$

EqualTo Compare two fields The value is usually used in scenarios such as entering a password twice. You can write the parameter fieldname, but note that it is a string variable pointing to the field name of another field in the same form

IPAddress Verify IPv4 address, parameters Default ipv4=True, ipv6=False. If you want to verify ipv6, you can set these two parameters in reverse.

Length Verify the length of the input string. You can have two parameters min and max to indicate the lower limit and upper limit of the length to be set. Note that the parameter type is a string, not INT!!

NumberRange To verify whether the input number is within the range, you can have two parameters, min and max, to indicate the upper and lower limits of the number. Note that the parameter type is a string, not INT!! Then you can set %(min)s and %( in the message parameter of this validator max)s two formatting parts to tell the front end what this range is. Other validators also have similar tricks, you can refer to the source code.

Optional Skip other validation functions in the same field when there is no input value

Required Required field

Regexp Use regular expression to verify the value, parameter regex='regular pattern'

URL To verify the URL, the required regular pattern is ^[a-z] ://(?P³ )(?P:[0-9] )?(?P/.*)?$

AnyOf Make sure the value is in the list of optional values. The parameters are values ​​(a list of optional values). In particular, when used in conjunction with SelectField, I don't know why the value of the items in SelectField's choices cannot be a number. . Otherwise, even if there are relevant numbers in the values ​​parameter of AnyOf, it cannot be recognized that the current option is a legal option. I suspect NoneOf may have the same trick.

NoneOf Make sure the value is not in the list of optional values

#forms.py文件：用来设定规则
from flask_wtf import FlaskForm
from flask_wtf.file import FileRequired, FileAllowed
from wtforms import StringField, PasswordField, SubmitField, FileField
from wtforms.validators import DataRequired, Length


class LoginForm(FlaskForm):
    name = StringField(
        label="用户名/邮箱/手机号",
        validators=[
            # DataRequired("请输入用户名"),
            Length(3, 20, message="长度不符"),
        ]
    )
    passwd = PasswordField(
        label="密码",
        validators=[
            # DataRequired("请输入密码"),
            Length(3, 20),
        ], )

    file = FileField(
        label="简历",
        validators=[
            FileRequired(),
            FileAllowed(['pdf', 'txt'], 'pdf 能被接收')
        ]
    )

#templates/demo/login.html
nbsp;html>


    <meta>
    <title>Title</title>

    {{ form.hidden_tag() }}     {{ form.name.label }} {{ form.name }}     {{ form.passwd.label }} {{ form.passwd }}     {{ form.file }}     

#主程序
import random
from flask import Flask, redirect, render_template
from forms import LoginForm
from flask_bootstrap import  Bootstrap

app = Flask(__name__)
bootstrap = Bootstrap(app)
app.config['SECRET_KEY'] =  random._urandom(24)

@app.route('/success/')
def success():
    return  "success"

@app.route('/login/', methods=('GET', 'POST'))
def submit():
    # 实例化表单对象;
    form = LoginForm()
    if form.validate_on_submit():
        print(form.data)
        return redirect('/success/')
    return render_template('demo/login.html', form=form)
app.run()

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