{"id":11959,"date":"2024-11-28T16:05:11","date_gmt":"2024-11-28T16:05:11","guid":{"rendered":"https:\/\/www.blopig.com\/blog\/?p=11959"},"modified":"2024-11-28T16:12:09","modified_gmt":"2024-11-28T16:12:09","slug":"building-cli-applications-with-typer","status":"publish","type":"post","link":"https:\/\/www.blopig.com\/blog\/2024\/11\/building-cli-applications-with-typer\/","title":{"rendered":"Building CLI Applications with Typer"},"content":{"rendered":"\n

Remember the last time you had to build a command-line tool? If you’re like me, you probably started with argparse<\/code> or click<\/code>, wrote boilerplate code, and still ended up with something that felt clunky. That’s where typer<\/a> comes in \u2013 it’s a game-changer that lets you build CLI apps with minimal code. Although there are several other options, typer stands out because it leverages Python’s type hints to do the heavy lifting. No more manual argument parsing! The following snippet shows how to use typer in its simplest form:<\/p>\n\n\n\n

import typer\n\napp = typer.Typer()\n\n@app.command()\ndef hello(name: str):\n    typer.echo(f\"Hello {name}!\")\n\nif __name__ == \"__main__\":\n    app()<\/pre>\n\n\n\n
And you will be able to execute it with just:<\/p>\n\n\n\n
$ python hello.py Pedro\nHello Pedro!\n\n<\/pre>\n\n\n\n
In this simple example, we were only defining positional arguments, but having optional arguments is as easy as setting default values in the function signature.<\/p>\n\n\n\n\n\n\n\n
import typer\n\napp = typer.Typer()\n\n@app.command()\ndef hello2(\n    name: str,\n    count: int = 1,\n    favorite_color: str = None\n):\n    for _ in range(count):\n        message = f\"Hello {name}!\"\n        if favorite_color:\n            message += f\" I like {favorite_color} too!\"\n        typer.echo(message)\n\nif __name__ == \"__main__\":\n    app()<\/pre>\n\n\n\n
$ python hello2.py --help\n\n Usage: hello2.py [OPTIONS] NAME                                                                                                               \n                                                                                                                                                   \n\u256d\u2500 Arguments \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\n\u2502 *    name      TEXT  [default: None] [required]                                                                  \n\u2570\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\n\u256d\u2500 Options \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\n\u2502 --count                     INTEGER  [default: 1]                                                                     \n\u2502 --favorite-color            TEXT     [default: None]                                                                  \n\u2502 --install-completion                 Install completion for the current shell.                                       \n\u2502 --show-completion                    Show completion for the current shell, to copy it or customize the installation.  \n\u2502 --help                               Show this message and exit.                                                       \n\u2570\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\n\n\n\n<\/pre>\n\n\n\n
And you can also provide additional metadata, like preferred parameter names or  help information by using the Annotated<\/code> type hint in combination with typer.Argument<\/code> for positional arguments and typer.Option<\/code> for optional arguments. And it also allows for some very useful options such as file path validation.<\/p>\n\n\n\n
from pathlib import Path\nimport typer\n\nfrom typing import Annotated\n\napp = typer.Typer()\n\n@app.command()\ndef process(\n    input_file: Annotated[\n        Path,\n        typer.Argument(\n            exists=True,\n            file_okay=True,\n            dir_okay=False,\n            help=\"Input file to process\"\n        )\n    ],\n    output_dir: Annotated[\n        Path,\n        typer.Option(\n            \"--output\",\n            \"-o\",\n            help=\"Output directory\",\n        )\n    ] = Path(\"output\"),\n    backup: Annotated[\n        bool,\n        typer.Option(\n            help=\"Create backup before processing\"\n        )\n    ] = False,\n):\n    \"\"\"Process a file with progress tracking.\"\"\"\n    \n    # Ensure output directory exists\n    output_dir.mkdir(parents=True, exist_ok=True)\n    \n    # Create backup if requested\n    if backup:\n        backup_file = output_dir \/ f\"{input_file.name}.bak\"\n        typer.echo(f\"Creating backup at {backup_file}\")\n        backup_file.write_bytes(input_file.read_bytes())\n    n = 0\n    with open(input_file) as f:\n        for line in f:\n            n+= len(line)\n    with open(output_dir \/ \"count.txt\", \"w\") as f:\n        f.write(f\"{n}\\n\")\n    \n    typer.echo(f\"Processing complete! N lines= {n}\")\n    \n\nif __name__ == \"__main__\":\n    app()<\/pre>\n\n\n\n
Whether you’re building a simple utility or a complex CLI application, typer’s type-driven approach will save you time and result in better tools. Next time you need to build a CLI tool, give typer a try. Your users (and future self) will thank you!<\/p>\n\n\n\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
Remember the last time you had to build a command-line tool? If you’re like me, you probably started with argparse or click, wrote boilerplate code, and still ended up with something that felt clunky. That’s where typer comes in \u2013 it’s a game-changer that lets you build CLI apps with minimal code. Although there are […]<\/p>\n","protected":false},"author":85,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","wikipediapreview_detectlinks":true,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"ngg_post_thumbnail":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[29,227],"tags":[809,152],"ppma_author":[557],"class_list":["post-11959","post","type-post","status-publish","format-standard","hentry","category-code","category-python-code","tag-cli","tag-python"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"authors":[{"term_id":557,"user_id":85,"is_guest":0,"slug":"ruben","display_name":"Ruben Sanchez-Garcia","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/7301ee01be22b8e41f73a40f0f9a3c1a8fcc9bd35f6ed27763b3827f56e8735c?s=96&d=mm&r=g","0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_links":{"self":[{"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/posts\/11959","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/users\/85"}],"replies":[{"embeddable":true,"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/comments?post=11959"}],"version-history":[{"count":5,"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/posts\/11959\/revisions"}],"predecessor-version":[{"id":12005,"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/posts\/11959\/revisions\/12005"}],"wp:attachment":[{"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/media?parent=11959"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/categories?post=11959"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/tags?post=11959"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.blopig.com\/blog\/wp-json\/wp\/v2\/ppma_author?post=11959"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}