Flask框架中的信号基于blinker，其主要就是让开发者可是在flask请求过程中定制一些用户行为。
pip3 install blinker
使用方法
from flask.signals import request_started
def func1(*args):
print(111, *args)
def func2(*args):
print(222, *args)
request_started.connect(func1) # 将函数注册到信号中
request_started.connect(func2)
request_started.send() # 触发这个信号，执行列表中的所有函数
内置信号
request_started = _signals.signal('request-started') # 请求到来前执行
request_finished = _signals.signal('request-finished') # 请求结束后执行
before_render_template = _signals.signal('before-render-template') # 模板渲染前执行
template_rendered = _signals.signal('template-rendered') # 模板渲染后执行
got_request_exception = _signals.signal('got-request-exception') # 请求执行出现异常时执行
request_tearing_down = _signals.signal('request-tearing-down') # 请求执行完毕后自动执行（无论成功与否）
appcontext_tearing_down = _signals.signal('appcontext-tearing-down')# 请求上下文执行完毕后自动执行（无论成功与否）
appcontext_pushed = _signals.signal('appcontext-pushed') # 请求上下文push时执行
appcontext_popped = _signals.signal('appcontext-popped') # 请求上下文pop时执行
message_flashed = _signals.signal('message-flashed') # 调用flask在其中添加数据时，自动触发
源码示例
appcontext_pushed：请求上下文push时触发
wsgi_app -- ctx.push() -- app_ctx.push()
class AppContext(object):
def push(self):
"""Binds the app context to the current context."""
self._refcnt += 1
if hasattr(sys, 'exc_clear'):
sys.exc_clear()
_app_ctx_stack.push(self)
# ############## 触发 appcontext_pushed 信号 ##############
appcontext_pushed.send(self.app)
request_started：在 @before_request之前
wsgi_app -- full_dispatch_request
class Flask(_PackageBoundObject):
def full_dispatch_request(self):
self.try_trigger_before_first_request_functions()
try:
# ############### 触发request_started 信号 ###############
request_started.send(self)
rv = self.preprocess_request()
if rv is None:
rv = self.dispatch_request()
except Exception as e:
rv = self.handle_user_exception(e)
return self.finalize_request(rv)
request_finished：在@after_request之后
wsgi_app -- full_dispatch_request -- finalize_request
class Flask(_PackageBoundObject):
def finalize_request(self, rv, from_error_handler=False):
response = self.make_response(rv)
try:
response = self.process_response(response)
# ############### request_finished 信号 ###############
request_finished.send(self, response=response)
except Exception:
if not from_error_handler:
raise
self.logger.exception('Request finalizing failed with an '
'error while handling an error')
return response
before_render_template 和 template_rendered：在模板渲染时触发
render_template -- _render
def render_template(template_name_or_list, **context):
ctx = _app_ctx_stack.top
ctx.app.update_template_context(context)
return _render(ctx.app.jinja_env.get_or_select_template(template_name_or_list),
context, ctx.app)
def _render(template, context, app):
# ############### before_render_template 信号 ###############
before_render_template.send(app, template=template, context=context)
rv = template.render(context)
# ############### template_rendered 信号 ###############
template_rendered.send(app, template=template, context=context)
return rv
got_request_exception ：在视图函数前后的过程中遇到异常时触发
wsgi_app -- handle_exception
class Flask(_PackageBoundObject):
def handle_exception(self, e):
exc_type, exc_value, tb = sys.exc_info()
# ############### 触发got_request_exception 信号 ###############
got_request_exception.send(self, exception=e)
handler = self._find_error_handler(InternalServerError())
if self.propagate_exceptions:
if exc_value is e:
reraise(exc_type, exc_value, tb)
else:
raise e
self.log_exception((exc_type, exc_value, tb))
if handler is None:
return InternalServerError()
return self.finalize_request(handler(e), from_error_handler=True)
request_tearing_down 和 appcontext_tearing_down：在wsgi_app最后触发
wsgi_app -- ctx.auto_pop() -- ctx.pop() -- app.do_teardown_request() -- app_ctx.pop(exc)
class RequestContext(object):
def pop(self, exc=_sentinel):
app_ctx = self._implicit_app_ctx_stack.pop()
try:
clear_request = False
if not self._implicit_app_ctx_stack:
self.preserved = False
self._preserved_exc = None
if exc is _sentinel:
exc = sys.exc_info()[1]
# ################## 触发 request_tearing_down 信号 ##################
self.app.do_teardown_request(exc)
if hasattr(sys, 'exc_clear'):
sys.exc_clear()
request_close = getattr(self.request, 'close', None)
if request_close is not None:
request_close()
clear_request = True
finally:
rv = _request_ctx_stack.pop()
# get rid of circular dependencies at the end of the request
# so that we don't require the GC to be active.
if clear_request:
rv.request.environ['werkzeug.request'] = None
# Get rid of the app as well if necessary.
if app_ctx is not None:
# ################## 触发 appcontext_tearing_down和appcontext_popped##################
app_ctx.pop(exc)
assert rv is self, 'Popped wrong request context. ' \
'(%r instead of %r)' % (rv, self)
class AppContext(object):
def pop(self, exc=_sentinel):
"""Pops the app context."""
try:
self._refcnt -= 1
if self._refcnt <= 0:
if exc is _sentinel:
exc = sys.exc_info()[1]
# ################## 触发 appcontext_tearing_down##################
self.app.do_teardown_appcontext(exc)
finally:
rv = _app_ctx_stack.pop()
assert rv is self, 'Popped wrong app context. (%r instead of %r)' \
% (rv, self)
# ################## 触发 appcontext_popped##################
appcontext_popped.send(self.app)
class Flask(_PackageBoundObject):
def do_teardown_request(self, exc=_sentinel):
if exc is _sentinel:
exc = sys.exc_info()[1]
funcs = reversed(self.teardown_request_funcs.get(None, ()))
bp = _request_ctx_stack.top.request.blueprint
if bp is not None and bp in self.teardown_request_funcs:
funcs = chain(funcs, reversed(self.teardown_request_funcs[bp]))
for func in funcs:
func(exc)
# ################## 触发 request_tearing_down 信号 ##################
request_tearing_down.send(self, exc=exc)
def do_teardown_appcontext(self, exc=_sentinel):
if exc is _sentinel:
exc = sys.exc_info()[1]
for func in reversed(self.teardown_appcontext_funcs):
func(exc)
# ################## 触发 appcontext_tearing_down信号 ##################
appcontext_tearing_down.send(self, exc=exc)
message_flashed：在调用flash函数时触发
def flash(message, category='message'):
flashes = session.get('_flashes', [])
flashes.append((category, message))
session['_flashes'] = flashes
# ############### 触发 message_flashed 信号 ###############
message_flashed.send(current_app._get_current_object(),
message=message, category=category)
自定义信号
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flask, current_app, flash, render_template
from flask.signals import _signals
app = Flask(import_name=__name__)
# 自定义信号
xxxxx = _signals.signal('xxxxx')
def func(sender, *args, **kwargs):
print(sender)
# 自定义信号中注册函数
xxxxx.connect(func)
@app.route("/x")
def index():
# 触发信号
xxxxx.send('123123', k1='v1')
return 'Index'
if __name__ == '__main__':
app.run()