1. Form组件扩展：

    1.简单扩展
        利用Form组件自带的正则扩展：
            a. 方式一
                from django.forms import Form
                from django.forms import widgets
                from django.forms import fields
                from django.core.validators import RegexValidator
                 
                class MyForm(Form):
                    user = fields.CharField(
                        error_messages={'invalid': '...'},
                        validators=[RegexValidator(r'^[0-9]+$', '请输入数字'), RegexValidator(r'^159[0-9]+$', '数字必须以159开头')],
                    )
            b. 方式二
                from django.forms import Form
                from django.forms import widgets
                from django.forms import fields
                from django.core.validators import RegexValidator
                 
                class MyForm(Form):
                    user = fields.RegexField(r'^[0-9]+$',error_messages={'invalid': '...'})