从flask学习笔记(四)：一个完整的flask程序 中，我们看见了app这个变量，现在我们来深入学习一下到底什么是app?
一、app的产生
1. 创建一个app
从上一节中，不难看出，app是由Flask类的对象。
# 实例化Flask对象
app = Flask(__name__)
2. Flask类部分源码
下面来学习一下Flask类的源码，探究一下什么是Flask 类。
# Flask类的初始化函数部分源码:
def __init__(
self,
import_name,
static_url_path=None,
static_folder="static",
static_host=None,
host_matching=False,
subdomain_matching=False,
template_folder="templates",
instance_path=None,
instance_relative_config=False,
root_path=None,
):
...
-
import name: 导入路径（寻找静态目录与模板位置的参数的参照路径变量） -
static_url_path="/python"：访问静态资源的url前缀，查找文件还是在static查找，但是url查找文件就是/python了，而不是static，默认值是static -
static_folder="static"：静态文件的目录，默认是static -
template_folder='templates'：模板的目录，默认是templates
二、 app.run()
1. 启动app
app.run(host="0.0.0.0", port=5000)
这是启动app的方法，如果不指定host和port，host默认为127.0.0.1，port默认为5000
2. app.run源码
下面看看run方法的源码
# 这是Flask类的对象方法，然后app调用这个方法了
def run(self, host=None, port=None, debug=None, load_dotenv=True, **options):
# Change this into a no-op if the server is invoked from the
# command line. Have a look at cli.py for more information.
if os.environ.get("FLASK_RUN_FROM_CLI") == "true":
from .debughelpers import explain_ignored_app_run
explain_ignored_app_run()
return
if get_load_dotenv(load_dotenv):
cli.load_dotenv()
# if set, let env vars override previous values
if "FLASK_ENV" in os.environ:
self.env = get_env()
self.debug = get_debug_flag()
elif "FLASK_DEBUG" in os.environ:
self.debug = get_debug_flag()
# debug passed to method overrides all other sources
if debug is not None:
self.debug = bool(debug)
_host = "127.0.0.1"
_port = 5000
server_name = self.config.get("SERVER_NAME")
sn_host, sn_port = None, None
if server_name:
sn_host, _, sn_port = server_name.partition(":")
host = host or sn_host or _host
# pick the first value that's not None (0 is allowed)
port = int(next((p for p in (port, sn_port) if p is not None), _port))
options.setdefault("use_reloader", self.debug)
options.setdefault("use_debugger", self.debug)
options.setdefault("threaded", True)
cli.show_server_banner(self.env, self.debug, self.name, False)
from werkzeug.serving import run_simple
try:
run_simple(host, port, self, **options)
finally:
# reset the first request information if the development server
# reset normally. This makes it possible to restart the server
# without reloader and that stuff from an interactive shell.
self._got_first_request = False
三、 app.url_map查看所有路由
1. url_map应用举例
from flask import Flask, current_app
app = Flask(__name__)
@app.route('/')
def hello_world():
return 'Hello World!'
if __name__ == '__main__':
print(app.url_map)
app.run()
输出
/Users/yuanjun/.virtualenvs/flask_py3/bin/python /Users/yuanjun/PycharmProject/code/app.py
Map([<Rule '/' (OPTIONS, GET, HEAD) -> hello_world>,
<Rule '/static/<filename>' (OPTIONS, GET, HEAD) -> static>])
* Serving Flask app "app" (lazy loading)
* Environment: production
WARNING: This is a development server. Do not use it in a production deployment.
Use a production WSGI server instead.
* Debug mode: on
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
* Restarting with stat
Map([<Rule '/' (HEAD, OPTIONS, GET) -> hello_world>,
<Rule '/static/<filename>' (HEAD, OPTIONS, GET) -> static>])
* Debugger is active!
* Debugger PIN: 251-856-449
2. 说明
Map([<Rule '/' (HEAD, OPTIONS, GET) -> hello_world>,
<Rule '/static/<filename>' (HEAD, OPTIONS, GET) -> static>])
生成一个Map映射关系列表每一个映射以Rule开始后面跟上路径规则括号里面是该视图支持的HTTP请求方法->指明视图函数（static是flask自己帮我们实现的）
3. url_map的源码
self.url_map = self.url_map_class()
self.url_map.host_matching = host_matching
self.subdomain_matching = subdomain_matching
url_map_class = Map
class Map(object):
#: A dict of default converters to be used.
default_converters = ImmutableDict(DEFAULT_CONVERTERS)
def __init__(
self,
rules=None,
default_subdomain="",
charset="utf-8",
strict_slashes=True,
redirect_defaults=True,
converters=None,
sort_parameters=False,
sort_key=None,
encoding_errors="replace",
host_matching=False,
):
self._rules = []
self._rules_by_endpoint = {}
self._remap = True
self._remap_lock = Lock()
self.default_subdomain = default_subdomain
self.charset = charset
self.encoding_errors = encoding_errors
self.strict_slashes = strict_slashes
self.redirect_defaults = redirect_defaults
self.host_matching = host_matching
self.converters = self.default_converters.copy()
if converters:
self.converters.update(converters)
self.sort_parameters = sort_parameters
self.sort_key = sort_key
for rulefactory in rules or ():
self.add(rulefactory)
def is_endpoint_expecting(self, endpoint, *arguments):
self.update()
arguments = set(arguments)
for rule in self._rules_by_endpoint[endpoint]:
if arguments.issubset(rule.arguments):
return True
return False
def iter_rules(self, endpoint=None):
self.update()
if endpoint is not None:
return iter(self._rules_by_endpoint[endpoint])
return iter(self._rules)
def add(self, rulefactory):
for rule in rulefactory.get_rules(self):
rule.bind(self)
self._rules.append(rule)
self._rules_by_endpoint.setdefault(rule.endpoint, []).append(rule)
self._remap = True
def bind(
self,
server_name,
script_name=None,
subdomain=None,
url_scheme="http",
default_method="GET",
path_info=None,
query_args=None,
):
server_name = server_name.lower()
if self.host_matching:
if subdomain is not None:
raise RuntimeError("host matching enabled and a subdomain was provided")
elif subdomain is None:
subdomain = self.default_subdomain
if script_name is None:
script_name = "/"
if path_info is None:
path_info = "/"
try:
server_name = _encode_idna(server_name)
except UnicodeError:
raise BadHost()
return MapAdapter(
self,
server_name,
script_name,
subdomain,
url_scheme,
path_info,
default_method,
query_args,
)
def bind_to_environ(self, environ, server_name=None, subdomain=None):
environ = _get_environ(environ)
wsgi_server_name = get_host(environ).lower()
if server_name is None:
server_name = wsgi_server_name
else:
server_name = server_name.lower()
if subdomain is None and not self.host_matching:
cur_server_name = wsgi_server_name.split(".")
real_server_name = server_name.split(".")
offset = -len(real_server_name)
if cur_server_name[offset:] != real_server_name:
# This can happen even with valid configs if the server was
# accesssed directly by IP address under some situations.
# Instead of raising an exception like in Werkzeug 0.7 or
# earlier we go by an invalid subdomain which will result
# in a 404 error on matching.
subdomain = "<invalid>"
else:
subdomain = ".".join(filter(None, cur_server_name[:offset]))
def _get_wsgi_string(name):
val = environ.get(name)
if val is not None:
return wsgi_decoding_dance(val, self.charset)
script_name = _get_wsgi_string("SCRIPT_NAME")
path_info = _get_wsgi_string("PATH_INFO")
query_args = _get_wsgi_string("QUERY_STRING")
return Map.bind(
self,
server_name,
script_name,
subdomain,
environ["wsgi.url_scheme"],
environ["REQUEST_METHOD"],
path_info,
query_args=query_args,
)
def update(self):
"""Called before matching and building to keep the compiled rules
in the correct order after things changed.
"""
if not self._remap:
return
with self._remap_lock:
if not self._remap:
return
self._rules.sort(key=lambda x: x.match_compare_key())
for rules in itervalues(self._rules_by_endpoint):
rules.sort(key=lambda x: x.build_compare_key())
self._remap = False
def __repr__(self):
rules = self.iter_rules()
return "%s(%s)" % (self.__class__.__name__, pformat(list(rules)))
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