Mike Driscoll Profile picture
Feb 18, 2022 โ€ข 11 tweets โ€ข 5 min read โ€ข Read on X
Today we are going to talk a little about creating command-line applications using #Python and its built-in `argparse` package!

๐Ÿงต๐Ÿ๐Ÿ‘‡
In this example of using `argparse`, you don't even create any custom arguments! You just create an ArgumentParser argument and call `print_help()`!

You can see in this example that `argparse` already provides useful information to your users without adding any arguments!
Normally when you create an `ArgumentParser` object, you would do so in a function and return the object.

Let's rewrite the previous example to follow that coding pattern:
Now let's add a required argument and a couple of optional arguments to our Python ArgumentParser!

To make an argument required, set `required=True`
Now let's try running your argparse example. Here are a few different examples of running your #Python command line app:
The previous examples only showed how to add short named arguments.

Here is an example that shows how you can have both a short name and a full or long named argument with `argparse`:
#Python's argparse module also supports creating mutually exclusive arguments. ๐Ÿ๐Ÿ”ฅ

Here is an example:
You can learn more about using Python's `argparse` by checking out my tutorial on @mousevspython

blog.pythonlibrary.org/2015/10/08/a-iโ€ฆ
@mousevspython A popular alternative to using #Python's built-in `argparse` module is a package called Click.

Click uses decorators and makes things even easier.

You can learn more here:

click.palletsprojects.com/en/8.0.x/
@mousevspython You may also want to check out the Python Fire package. It is a different kind of for package for automatically generating command line interfaces.

google.github.io/python-fire/
@mousevspython Thanks for reading my thread on creating command-line interfaces with #Python!

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More from @driscollis

Feb 1
Did you know that #Python supports SQLite in the standard library? That's right. You don't need to install anything! ๐Ÿ๐Ÿš€

Let's talk a little about that!

๐Ÿงต๐Ÿ‘‡
If you have a pre-existing SQLite database file, you can use #Python's `sqlite3` module to connect to it

Here's how: Image
If you want to create a new SQLite database with #Python, you can use the same syntax that you'd use to connect to a pre-existing one.

Then create a cursor object and create your table, like this: Image
Read 8 tweets
Nov 21, 2023
Today is a great day to talk about #Python lambdas!

Let's learn about them in a thread

๐Ÿ๐Ÿงต๐Ÿ‘‡
A Python lambda is a one-line anonymous function.

Rule #1 is do NOT assign a lambda to a variable.

When you do that, it's no longer an anonymous function. You should just create a regular function at that point Image
If you want to run a lambda in your REPL, wrap it in parentheses, like this: Image
Read 9 tweets
Mar 23, 2023
Want to create a copy of a #Python list? Use Python's `copy()` method!

Note: Watch out if your list contains lists of dictionaries. In those cases, you might be better off using copy.deepcopy()
But be careful! If your list contains a mutable object, like another list or a dictionary, you may encounter some unexpected behavior.

In the following example, you `copy()` the list. Then you modify the nested dictionary in the copy, but that also changes the original list!
You can fix this behavior by using Python's `copy` module. It provides a deepcopy() function that you can use which will make a deep copy of the ENTIRE list!
Read 4 tweets
Mar 22, 2023
#Python generators aren't talked about enough.

So let's talk about them today!

๐Ÿงต๐Ÿ๐Ÿ‘‡
According to the #Python wiki, "Generator functions allow you to declare a function that behaves like an iterator"

One of their best use cases is to chunk through large data sets a piece at a time, which prevents you from running out of memory.

wiki.python.org/moin/Generators
To create a generator in #Python, you need to use the `yield` keyword instead of `return` inside a function.

Generators will continue to yield values until the generator is exhausted.

The following example will continue to yield numbers for as long as you call it: Image
Read 10 tweets
Mar 21, 2023
My 11th #Python book is now available! ๐Ÿ๐Ÿคฏ

Test your Python skills and knowledge with over 100 PYthon quizzes. Answers are included if you get stuck!

Available on Amazon, Leanpub, and Gumroad (see following tweets)
Get my 11th #Python book, The Python Quiz book on Amazon in the following formats:

๐Ÿ Kindle
๐Ÿ Paperback

amazon.com/dp/B0BVT8DZV1
You can find The Python Quiz Book on @gumroad too in the following formats:

๐Ÿ epub
๐Ÿ PDF

driscollis.gumroad.com/l/pyquiz
Read 4 tweets
Mar 17, 2023
Starting in Python 3.7, the `breakpoint()` built-in function was added

It is defined in PEP 553 and simplifies adding a breakpoint to your code

#python_builtins_by_driscollis

๐Ÿงต๐Ÿ๐Ÿ‘‡
You can read about the `breakpoint()` function for Python here:

python.org/dev/peps/pep-0โ€ฆ
Here is some sample code showing how to use the `breakpoint()` function in your Python code
Read 6 tweets

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