Python Print Line Number In File' title='Python Print Line Number In File' />Comparing Python Command Line Parsing Libraries Argparse, Docopt, and Click. About a year ago I began a job where building command line applications was a common occurrence. At that time I had used argparse quite a bit and wanted to explore what other options were available. I found that the most popular alternatives available were click and docopt. During my exploration I also found that other than each libraries why use me section there was not much available for a complete comparison of the three libraries. Now there is this blog post This is a guest blog post by Kyle Purdon, an Application Engineer at Bitly in Denver. If you want to, you can head directly to the source though it really wont do much good without the comparisons and step by step construction presented in this article. This article uses the following versions of the libraries 1. Python core library pip list grep click. Command Line Example. The command line application that we are creating will have the following interface python file. NAMEBasic Usage. 12. Kyle. python file. Python Print Line Number In File' title='Python Print Line Number In File' />Kyle. Usage w Options Flags1. Wazzup Kyle. python file. Later Kyle. python file. Kyle. python file. Wazzup caps Kyle. This article will compare each libraries method for implementing the following features Commands hello, goodbyeArguments nameOptionsFlags greetinglt str, capsAdditional features Version Printing v versionAutomated Help Messages. Error Handling. As you would expect argparse, docopt, and click implement all of these features as any complete command line library would. Php The mbstring package adds UTF8 aware string functions with mb prefixes. We assume that os, re, and sys are always imported. Grammar and Execution. CommandLine Example. The commandline application that we are creating will have the following interface python file. NAME. The line above, which again should work for Linux or Mac, will open a new file in vim, the commandline text editor that I prefer. You can follow along, or feel free. This fact means that the actual implementation of these features is what we will compare. Each library takes a very different approach that lends to a very interesting comparison argparsestandard, docoptdocstrings, clickdecorators. Bonus Sections. Ive been curious about using task runner libraries like fabric and its python. I will try and put the same interface together with invoke. A few extra steps are needed when packaging command line applications, so Ill cover those steps as well Commands. Lets begin by setting up the basic skeleton no arguments or options for each library. Argparse. 12. 34. Argument. Parsersubparsersparser. With this we now have two commands hello and goodbye and a built in help message. Notice that the help message changes when run as an option on the command hello. Docopt. 12. 34. 56. Greeter. Usage commands. Options h help Show this screen. With this we, again, have two commands hello, goodbye and a built in help message. Notice that the help message DOES NOT change when run as an option on the hello command. In addition we do not need to explicitly specify the commands. Options section to get a help command. However, if we dont they will not show up in the output help message as options. Show this screen. Show this screen. Click. 12. 34. 56. With this we now have two commands hello, goodbye and a built in help message. Notice that the help message changes when run as an option on the hello command. Usage commands. py OPTIONS COMMAND ARGS. Show this message and exit. Usage commands. py hello OPTIONSOptions. Show this message and exit. Even at this point you can see that we have very different approaches to constructing a basic command line application. Next lets add the NAME argument, and the logic to ouput the result from each tool. Arguments. In this section we will be adding new logic to the same code shown in the previous section. Well add comments to new lines stating their purpose. Arguments aka positional arguments are required inputs to a command line application. In this case we are adding a required name argument so that the tool can greet a specific person. Argparse. To add an argument to a subcommand we use the addargument method. And in order to execute the correct logic, when a command is called, we use the setdefaults method to set a default function. Finally we execute the default function by calling args. Hello, 0. formatargs. Goodbye, 0. formatargs. Argument. Parsersubparsersparser. Kyle. python argparsearguments. Docopt. In order to add an option, we add a lt name to the docstring. The lt are used to designate a positional argument. In order to execute the correct logic we must check if the command treated as an argument is True at runtime if argumentshello, then call the correct function. Arcgis 10 Keygen. Greeter. Usage basic. Options h help Show this screen. Hello, 0. Goodbye, 0. Kyle. python docoptarguments. Options. h help Show this screen. Note that the help message is not specific to the subcommand, rather it is the entire docstring for the program. Click. In order to add an argument to a click command we use the click. In this case we are just passing the argument name, but there are many more options some of which well use later. Since we are decorating the logic function with the argument we dont need to do anything to set or make a call to the correct logic. Hello, 0. formatkwargsnamegreet. Goodbye, 0. formatkwargsnameifnamemain greet1. Corel Draw 12 Portable Full. Kyle. python clickarguments. Usage arguments. OPTIONS NAME. Show this message and exit. FlagsOptions. In this section we will again be adding new logic to the same code shown in the previous section. Well add comments to new lines stating there purpose. Options are non required inputs that can be given to alter the execution of a command line application. Flags are a boolean only TrueFalse subset of options. For example foobar will pass bar as the value for the foo option and baz if defined as a flag will pass the value of True is the option is given, or False if not. For this example we are going to add the greetinggreeting option, and the caps flag. The greeting option will have default values of Hello and Goodbye and allow the user to pass in a custom greeting. For example given greetingWazzup the tool will respond with Wazzup, name The caps flag will uppercase the entire response if given. For example given caps the tool will respond with HELLO, NAME Argparse. Argument. Parsersubparsersparser. Hello add a flag defaultFalsehelloparser. Goodbyegoodbyeparser. Wazzup Kyle. python argparseoptions. Kyle. python argparseoptions. Wazzup caps Kyle. GREETING caps name. GREETING. Docopt. Once we hit the case of adding options with defaults, we hit a snag with the basic implementation of commands in docopt. Lets continue just to illustrate the issue. Greeter. Usage basic. Options h help Show this screen. Uppercase the output. Greeting to use default Hello. Now, see what happens when we run the following commands 1. Kyle. python docoptoptions. Kyle. What Because we can only set a single default for the greeting option both of our Hello and Goodbye commands now respond with Hello, Kyle In order for us to make this work well need to follow the git example docopt provides. The refactored code is shown below 1. Show this screen. Say hello goodbye Say goodbyefromdocoptimportdocopt. HELLOusage basic. Show this screen. Uppercase the output.