python - 关于Flask中全局变量问题
Q：看了一个Flask的简单教程，但是有一个问题不明白。Flask中app的全局变量在多个客户端访问的情况下不会出错吗?
比如下面代码中tasks列表在多个客户端同时访问的时候不会出错吗？我用两个客户端进行删除操作的时候，没有发现问题，但是在并发更高的情况下会不会出现问题，表示不理解，求解释。
PS：下面代码在python3.0中，需要把
task = filter(lambda t: t['id'] == task_id, tasks)
if len(task) == 0:
改成
task = filter(lambda t: t['id'] == task_id, tasks)
task = list(task)
if len(task) == 0:#!flask/bin/python
from flask import Flask, jsonify, abort, request, make_response, url_for
from flask.ext.httpauth import HTTPBasicAuth
app = Flask(__name__, static_url_path = "")
auth = HTTPBasicAuth()
@auth.get_password
def get_password(username):
if username == 'miguel':
return 'python'
return None
@auth.error_handler
def unauthorized():
return make_response(jsonify( { 'error': 'Unauthorized access' } ), 403)
# return 403 instead of 401 to prevent browsers from displaying the default auth dialog
@app.errorhandler(400)
def not_found(error):
return make_response(jsonify( { 'error': 'Bad request' } ), 400)
@app.errorhandler(404)
def not_found(error):
return make_response(jsonify( { 'error': 'Not found' } ), 404)
tasks = [
{
'id': 1,
'title': u'Buy groceries',
'description': u'Milk, Cheese, Pizza, Fruit, Tylenol',
'done': False
},
{
'id': 2,
'title': u'Learn Python',
'description': u'Need to find a good Python tutorial on the web',
'done': False
}
]
def make_public_task(task):
new_task = {}
for field in task:
if field == 'id':
new_task['uri'] = url_for('get_task', task_id = task['id'], _external = True)
else:
new_task[field] = task[field]
return new_task
@app.route('/todo/api/v1.0/tasks', methods = ['GET'])
@auth.login_required
def get_tasks():
return jsonify( { 'tasks': map(make_public_task, tasks) } )
@app.route('/todo/api/v1.0/tasks/<int:task_id>', methods = ['GET'])
@auth.login_required
def get_task(task_id):
task = filter(lambda t: t['id'] == task_id, tasks)
if len(task) == 0:
abort(404)
return jsonify( { 'task': make_public_task(task[0]) } )
@app.route('/todo/api/v1.0/tasks', methods = ['POST'])
@auth.login_required
def create_task():
if not request.json or not 'title' in request.json:
abort(400)
task = {
'id': tasks[-1]['id'] + 1,
'title': request.json['title'],
'description': request.json.get('description', ""),
'done': False
}
tasks.append(task)
return jsonify( { 'task': make_public_task(task) } ), 201
@app.route('/todo/api/v1.0/tasks/<int:task_id>', methods = ['PUT'])
@auth.login_required
def update_task(task_id):
task = filter(lambda t: t['id'] == task_id, tasks)
if len(task) == 0:
abort(404)
if not request.json:
abort(400)
if 'title' in request.json and type(request.json['title']) != unicode:
abort(400)
if 'description' in request.json and type(request.json['description']) is not unicode:
abort(400)
if 'done' in request.json and type(request.json['done']) is not bool:
abort(400)
task[0]['title'] = request.json.get('title', task[0]['title'])
task[0]['description'] = request.json.get('description', task[0]['description'])
task[0]['done'] = request.json.get('done', task[0]['done'])
return jsonify( { 'task': make_public_task(task[0]) } )
@app.route('/todo/api/v1.0/tasks/<int:task_id>', methods = ['DELETE'])
@auth.login_required
def delete_task(task_id):
task = filter(lambda t: t['id'] == task_id, tasks)
if len(task) == 0:
abort(404)
tasks.remove(task[0])
return jsonify( { 'result': True } )
if __name__ == '__main__':
app.run(debug = True)项目链接
