For many years the famous “Hello, World” example Flask application was 7 lines long. Below you can see a snapshot of the Flask website as it looked on June 12th, 2017:
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- How To Run Flask App On Mac Pro
- How To Run Flask App On Mac High Sierra
- Run Flask App On Ec2
Install heroku on your device using Terminal whether you use mac or widows or ubunto heroku has provided instruction to install it through all of them you can check the instructions from here. In this video I start with a simple Python Flask application and show how to 1) Write a Dockerfile 2) Build docker image 3) Start running a docker container based off the image In the end we have. The Python Flask app with have a new URL route. We have changed the default port to 80, the default HTTP port: from flask import Flask, flash, redirect, rendertemplate, request, session, abort. Vent app for mac. Flask will detect and use them if you install them. Blinker provides support for Signals. SimpleJSON is a fast JSON implementation that is compatible with Python’s json module. It is preferred for JSON operations if it is installed. Python-dotenv enables support for Environment Variables From dotenv when running flask commands.
This example application then was shortened to just 5 lines. Here is the same page on June 17th, 2017:
As you can see, the core of the application has not changed, but the method by which the application server is started has indeed changed, and in a very significant way. While previously a simple
app.run()
call inside the application script was used, now there is a flask run
command, plus a FLASK_APP
environment variable.While the design of the Flask website has changed considerably in the years that followed, as I’m writing this article in 2020 the
flask run
method continues to be the most visible in the official documentation for the framework.Today you can still find a large number of applications and code tutorials that use the
app.run()
method. One reason for this is that there is a lot of older but otherwise still relevant content out there for Flask. But also, a lot of people still see app.run()
as more convenient and easier to use.In this article we are going to explore the pros and cons of each of these methods. Ready? Let’s dive in!
Should I use app.run() or flask run?
We'll begin with the million dollar question. If you are starting a new Flask application today, should you use
app.run()
or flask run
?Unfortunately there isn’t a simple answer.
The most important thing you need to know is that both these methods start a development web server, which is a server that you will use locally on your own system while you develop your application. If you are trying to figure out how to start your application on a production server, then the answer is indeed simple: use neither. For a production deployment use a production-ready web server such as gunicorn or uWSGI.
In a development environment, both methods are fully supported, so you can use the one you like best. But of course, you probably want some help in deciding, so let’s look at both methods in detail.
Using flask run
The
flask run
method is the newest solution and is recommended by the Flask project.The
flask
command is added to your virtual environment when you install the Flask package. It comes out of the box with three commands:The Flask framework includes a command-line interface module that allows third-party Flask extensions or even your own application to install custom commands to complement the base three, making this a very powerful and extensible system for managing all aspects of your Flask application.
The tricky part about getting the
flask run
command to work is that somehow this command needs to figure out where your Flask application instance is located, so that it can import it and use it.How flask run
finds your application instance
The way the
flask run
command learns where your application is located is by setting the FLASK_APP
environment variable to point to it. There are actually five different ways this variable can be set:FLASK_APP='module:name'
: This is a fairly standard nomenclature for WSGI applications. If your application instance is calledapp
and is defined in a hello.py module, then you would setFLASK_APP='hello:app'
. Instead of a simple module you can specify a more complex import path in standard dotted notation, such asFLASK_APP='server.core:app'.
FLASK_APP='module:function()'
: If you use the application factory pattern in your application, you can specify the name of your factory function instead of an application name. Flask will import the function and call it to create the application. This form also supports passing arguments into the factory function, for exampleFLASK_APP='hello:create_app('dev')'
.FLASK_APP=module
: If you specify just an import path without an application name or factory function, then Flask will import your module or package and try to locate the application on its own. It will first look for anapp
orapplication
global variable, and if neither is found it will inspect all global variables in the module looking for one that is set to an instance of classFlask
. If none of these attempts produce an application, Flask will finally look for an application factory function in your module called eithercreate_app()
ormake_app()
. If Flask can’t still find your application, then theflask run
command will exit with an error.FLASK_APP=file.py
: If you have your application in a Python file, you can simply set the name of the file, and Flask will import it and find the application using the same rules as in the previous option.- If
FLASK_APP
is not defined, Flask will attempt to runimport app
andimport wsgi
. If either of these succeeds, it will then try to find the application in the imported module using the same rules as the previous two options.
If you are writing a short Flask application for a quick test, calling your Flask application instance
app
and putting it in an app.py file is enough to make flask run
work without having to worry about environment variables.Specifying server options
The flask run` command provides options to set the server listening IP address and port, SSL certificates, etc:
It is important to note that Flask’s debug mode cannot be specified through an option, and instead is set via
FLASK_ENV=development
in the environment.Using app.run()
How To Run Flask App On Mac Computer
After going through the many complexities of the
flask run
command you can probably guess why app.run()
hasn’t gone away.Windows 10 apps close automatically. With this method there is no issue with Flask knowing where your application instance is located, because you are directly invoking the
run()
method on this object. For this reason no environment variables are needed.Specifying server options
Quick notes app mac. The
app.run()
method supports several options, including all those you can provide to the flask run
command, and a few more:host
– the hostname to listen on.port
– the port of the web server.debug
– if given, enable or disable debug mode.load_dotenv
– load the nearest .env and .flaskenv files to set environment variables.use_reloader
– should the server automatically restart the python process if modules were changed?use_debugger
– should the werkzeug debugging system be used?use_evalex
– should the exception evaluation feature be enabled?extra_files
– a list of files the reloader should watch additionally to the modules.reloader_interval
– the interval for the reloader in seconds.reloader_type
– the type of reloader to use.threaded
– should the process handle each request in a separate thread?processes
– if greater than 1 then handle each request in a new process up to this maximum number of concurrent processes.passthrough_errors
– set this to True to disable the error catching.ssl_context
– an SSL context for the connection.
Disadvantages of app.run()
If you are thinking that
app.run()
seems to be a more convenient way to start your Flask application, consider the two main disadvantages this method has versus flask run
:- The reloader is less robust. Because the application needs to be imported before the
run()
method can be invoked, any errors that occur while importing the application cause the reloader to break and exit. Withflask run
, if the application fails to import due to an error, the reloader continues to watch the source files and attempts to import it again after you correct the mistake. - The
app.run()
command has no command-line interface.
Can’t decide? Use both!
What most people fail to realize is that there is no exclusive choice between the two methods, both can be used together without conflict. First, make sure your main application file invokes
app.run()
at the end:https://asnhyd.weebly.com/any-app-that-can-open-rar-files-on-mac.html. Then, set the
FLASK_APP
environment variable to point to this file. For example, if your file is called hello.py:Now you can start your application via
flask run
or python hello.py
. You have full access to the Flask CLI, while at the same time you can enjoy the convenience of running your own script when appropriate.Both methods can coexist happily!
Miguel Grinberg is a Python Developer for Technical Content at Twilio. Reach out to him at mgrinberg [at] twilio [dot] com if you have a cool Python project you’d like to share on this blog!
This is not a problem I thought I’d be running into any time soon, however, the nature of software development is such that unpredictable hurdles jump out at you at every stage of the development process.
Flask App Run Host
I like to primarily describe myself as a web developer. The largest projects I’ve worked on in the past have all been web-based. There are several reasons for my preference in developing for the web. Firstly, the web is universal. Almost every device with a screen these days has a web browser built-in. Developing for the web allows me to reach as many devices and people as possible with my work. In addition to that, the web has a universal language, I can pick whatever stack I want and as long as I have some HTML, JS and CSS in the front-end, the browser will understand what I’m trying to say to it. The opposite is true for desktop applications (if you want to develop them natively, at least). As you’d need to work with different languages, frameworks, and codebases in order to develop for different systems. Desktop apps do have their advantages though. For one, if you are planning on building a stand-alone application, building a web app and deploying it to a server makes little sense, you’d be better off creating an app that can be packaged, installed, and run locally on a target machine.
How To Run Flask App On Mac Pro
This brings us to the topic of this article. Recently, I have been working on some personal software projects. Nothing I plan on sharing with the world as it’s software that I plan on using to improve my daily activities. However, even if the software was to be released, it has no real need to exist on the web, as it is fully functional when running locally. As I came to this realisation in the middle of development, I decided to change my approach from creating a web app to a desktop app. Being very far along the development process, it wasn’t very feasible to restart the entire project, so I set off looking for a way to convert my current app into a desktop app with the current codebase.
The project in question is built on flask, a python micro-framework for building small web-apps. You could build large apps with it but I would recommend a larger framework like Django for that purpose. Flask is very straight forward in the way it works. You can get set up with just a few lines of code as follows:
The code above creates a flask app server that displays “Hello, world!” on the browser when you visit localhost at the specified port(usually 5000 by default). Simple and fast, but, this is a web app. In order to access this, you’d have to start the server, open the browser and then load its address. In order to turn this into a desktop application, I incorporated the use of the flask-desktop library. This library allows us to convert a flask application to a desktop one with a few lines of code.
We have only added three lines of code here: importing the webui library, creating a ui object and passing it our app object, and finally replacing app.run with ui.run. That’s it! Really, that’s all there is to it. This app should be able to run on Mac, Windows, and Linux. You can even create a standalone executable using PyInstaller. The front-end of the application can still be developed using HTML templates, JavaScript and CSS.
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