WTForms是一个支持多个web框架的form组件，主要用于对用户请求数据进行验证。
安装：
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pip3 install wtforms |
用户登录注册示例
1. 用户登录
当用户登录时候，需要对用户提交的用户名和密码进行多种格式校验。如：
用户不能为空；用户长度必须大于6；
密码不能为空；密码长度必须大于12；密码必须包含 字母、数字、特殊字符等（自定义正则）；
#!/usr/bin/env python # -*- coding:utf-8 -*- from flask import Flask, render_template, request, redirect from wtforms import Form from wtforms.fields import core from wtforms.fields import html5 from wtforms.fields import simple from wtforms import validators from wtforms import widgets app = Flask(__name__, template_folder=‘templates‘) app.debug = True class LoginForm(Form): name = simple.StringField( label=‘用户名‘, validators=[ validators.DataRequired(message=‘用户名不能为空.‘), validators.Length(min=6, max=18, message=‘用户名长度必须大于%(min)d且小于%(max)d‘) ], widget=widgets.TextInput(), render_kw={‘class‘: ‘form-control‘} ) pwd = simple.PasswordField( label=‘密码‘, validators=[ validators.DataRequired(message=‘密码不能为空.‘), validators.Length(min=8, message=‘用户名长度必须大于%(min)d‘), validators.Regexp(regex="^(?=.*[a-z])(?=.*[A-Z])(?=.*d)(?=.*[[email protected]$!%*?&])[A-Za-z[email protected]$!%*?&]{8,}", message=‘密码至少8个字符，至少1个大写字母，1个小写字母，1个数字和1个特殊字符‘) ], widget=widgets.PasswordInput(), render_kw={‘class‘: ‘form-control‘} ) @app.route(‘/login‘, methods=[‘GET‘, ‘POST‘]) def login(): if request.method == ‘GET‘: form = LoginForm() return render_template(‘login.html‘, form=form) else: form = LoginForm(formdata=request.form) if form.validate(): print(‘用户提交数据通过格式验证，提交的值为：‘, form.data) else: print(form.errors) return render_template(‘login.html‘, form=form) if __name__ == ‘__main__‘: app.run()
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <h1>登录</h1> <form method="post"> <!--<input type="text" name="name">--> <p>{{form.name.label}} {{form.name}} {{form.name.errors[0] }}</p> <!--<input type="password" name="pwd">--> <p>{{form.pwd.label}} {{form.pwd}} {{form.pwd.errors[0] }}</p> <input type="submit" value="提交"> </form> </body> </html>
示例下载：点击这里
3.meta
#!/usr/bin/env python # -*- coding:utf-8 -*- from flask import Flask, render_template, request, redirect, session from wtforms import Form from wtforms.csrf.core import CSRF from wtforms.fields import core from wtforms.fields import html5 from wtforms.fields import simple from wtforms import validators from wtforms import widgets from hashlib import md5 app = Flask(__name__, template_folder=‘templates‘) app.debug = True class MyCSRF(CSRF): """ Generate a CSRF token based on the user‘s IP. I am probably not very secure, so don‘t use me. """ def setup_form(self, form): self.csrf_context = form.meta.csrf_context() self.csrf_secret = form.meta.csrf_secret return super(MyCSRF, self).setup_form(form) def generate_csrf_token(self, csrf_token): gid = self.csrf_secret + self.csrf_context token = md5(gid.encode(‘utf-8‘)).hexdigest() return token def validate_csrf_token(self, form, field): print(field.data, field.current_token) if field.data != field.current_token: raise ValueError(‘Invalid CSRF‘) class TestForm(Form): name = html5.EmailField(label=‘用户名‘) pwd = simple.StringField(label=‘密码‘) class Meta: # -- CSRF # 是否自动生成CSRF标签 csrf = True # 生成CSRF标签name csrf_field_name = ‘csrf_token‘ # 自动生成标签的值，加密用的csrf_secret csrf_secret = ‘xxxxxx‘ # 自动生成标签的值，加密用的csrf_context csrf_context = lambda x: request.url # 生成和比较csrf标签 csrf_class = MyCSRF # -- i18n # 是否支持本地化 # locales = False locales = (‘zh‘, ‘en‘) # 是否对本地化进行缓存 cache_translations = True # 保存本地化缓存信息的字段 translations_cache = {} @app.route(‘/index/‘, methods=[‘GET‘, ‘POST‘]) def index(): if request.method == ‘GET‘: form = TestForm() else: form = TestForm(formdata=request.form) if form.validate(): print(form) return render_template(‘index.html‘, form=form) if __name__ == ‘__main__‘: app.run()
其他：
1. metaclass
class MyType(type): def __init__(self, *args, **kwargs): print(‘MyType创建类‘,self) super(MyType, self).__init__(*args, **kwargs) def __call__(self, *args, **kwargs): obj = super(MyType, self).__call__(*args, **kwargs) print(‘类创建对象‘, self, obj) return obj class Foo(object,metaclass=MyType): user = ‘wupeiqi‘ age = 18 obj = Foo()
class MyType(type): def __init__(self, *args, **kwargs): super(MyType, self).__init__(*args, **kwargs) def __call__(cls, *args, **kwargs): v = dir(cls) obj = super(MyType, cls).__call__(*args, **kwargs) return obj class Foo(MyType(‘MyType‘, (object,), {})): user = ‘wupeiqi‘ age = 18 obj = Foo()
class MyType(type): def __init__(self, *args, **kwargs): super(MyType, self).__init__(*args, **kwargs) def __call__(cls, *args, **kwargs): v = dir(cls) obj = super(MyType, cls).__call__(*args, **kwargs) return obj def with_metaclass(arg,base): return MyType(‘MyType‘, (base,), {}) class Foo(with_metaclass(MyType,object)): user = ‘wupeiqi‘ age = 18 obj = Foo()
2. 实例化流程分析
# 源码流程 1. 执行type的 __call__ 方法，读取字段到静态字段 cls._unbound_fields 中； meta类读取到cls._wtforms_meta中 2. 执行构造方法 a. 循环cls._unbound_fields中的字段，并执行字段的bind方法，然后将返回值添加到 self._fields[name] 中。 即： _fields = { name: wtforms.fields.core.StringField(), } PS：由于字段中的__new__方法，实例化时：name = simple.StringField(label=‘用户名‘)，创建的是UnboundField(cls, *args, **kwargs)，当执行完bind之后，才变成执行 wtforms.fields.core.StringField() b. 循环_fields，为对象设置属性 for name, field in iteritems(self._fields): # Set all the fields to attributes so that they obscure the class # attributes with the same names. setattr(self, name, field) c. 执行process，为字段设置默认值：self.process(formdata, obj, data=data, **kwargs) 优先级：obj,data,formdata; 再循环执行每个字段的process方法，为每个字段设置值： for name, field, in iteritems(self._fields): if obj is not None and hasattr(obj, name): field.process(formdata, getattr(obj, name)) elif name in kwargs: field.process(formdata, kwargs[name]) else: field.process(formdata) 执行每个字段的process方法，为字段的data和字段的raw_data赋值 def process(self, formdata, data=unset_value): self.process_errors = [] if data is unset_value: try: data = self.default() except TypeError: data = self.default self.object_data = data try: self.process_data(data) except ValueError as e: self.process_errors.append(e.args[0]) if formdata: try: if self.name in formdata: self.raw_data = formdata.getlist(self.name) else: self.raw_data = [] self.process_formdata(self.raw_data) except ValueError as e: self.process_errors.append(e.args[0]) try: for filter in self.filters: self.data = filter(self.data) except ValueError as e: self.process_errors.append(e.args[0]) d. 页面上执行print(form.name) 时，打印标签 因为执行了： 字段的 __str__ 方法 字符的 __call__ 方法 self.meta.render_field(self, kwargs) def render_field(self, field, render_kw): other_kw = getattr(field, ‘render_kw‘, None) if other_kw is not None: render_kw = dict(other_kw, **render_kw) return field.widget(field, **render_kw) 执行字段的插件对象的 __call__ 方法，返回标签字符串
3. 验证流程分析
a. 执行form的validate方法，获取钩子方法 def validate(self): extra = {} for name in self._fields: inline = getattr(self.__class__, ‘validate_%s‘ % name, None) if inline is not None: extra[name] = [inline] return super(Form, self).validate(extra) b. 循环每一个字段，执行字段的 validate 方法进行校验(参数传递了钩子函数) def validate(self, extra_validators=None): self._errors = None success = True for name, field in iteritems(self._fields): if extra_validators is not None and name in extra_validators: extra = extra_validators[name] else: extra = tuple() if not field.validate(self, extra): success = False return success c. 每个字段进行验证时候 字段的pre_validate 【预留的扩展】 字段的_run_validation_chain，对正则和字段的钩子函数进行校验 字段的post_validate【预留的扩展】