python cli tested with pytest - (beginner to intermediate) anthony explains

I build out a simple skeleton for a command line interface in python and show how to test it with pytest!
thanks to PanosTrak for the question!
playlist: • anthony explains
==========
twitch: / anthonywritescode
dicsord: / discord
twitter: / codewithanthony
github: github.com/aso...
stream github: github.com/ant...
I won't ask for subscriptions / likes / comments in videos but it really helps the channel. If you have any suggestions or things you'd like to see please comment below!

[@ShawkingIT]

Such a simple idea, but really enjoyed how you built it into a full script. Filled in blanks for me of how to test and use cases for raising exceptions. Great video. Thank you.

[@thomashirtz]

Saying that your videos are amazing would be an understatement :) thanks for the explanation!

[@anthonywritescode]

glad you're enjoying them!

[@defectdefect322]

ALL python coders should watch your videos

[@devopsislove]

thank you Anthony! You definitely have a talent for explaining complex things in simple language

[@grzegorzryznar5101]

I found ypur channel on the recommendation of a colleague and I am very glad, cause I have learned a lot of new things from these video! Thanks :)

[@anthonywritescode]

glad you're enjoying it!

[@GabrieleBonetti]

Continuing on the pytest path, an interesting advanced one would be fixtures and dependency injection
By the way, this is great content. Cheers

[@jrib]

I would love to see a video on the best/most common use cases for fixtures in pytest!

[@anthonywritescode]

I have plans to do a thing on fixtures at some point!

[@jrib]

@@anthonywritescode Nice! Looking forward to it.

[@pustemapustema6497]

I use python for five years , your videos are t h e best

[@selvakumars6487]

Awesome work, Thanks Anthony

[@starshipx1282]

a lot of very useful info presented very nicely. Thank you anthony.

[@nomik]

Awesome tutorial!

[@jimigrok]

nice explanation !

[@sadhlife]

any reason why you didn't import Optional and Sequence in a single line import?

[@anthonywritescode]

yep! that's covered in th-cam.com/video/Sjor8PZXnaw/w-d-xo.html

[@vinzent1992]

awesome quick intro to cli, learned some new stuff. How about talking about asyncio next? ;D

[@anthonywritescode]

I don't know that much about asyncio, but maybe I could do like a hello world program or something -- stay tuned!

[@vinzent1992]

@@anthonywritescode will definitely stay tuned 👍.. Hello worlds are plentiful though, am having a harder time finding useful real-world examples 😉..

[@ulfsjodin7872]

I found a very good example in this video: "testing output with pytest (beginner - intermediate) anthony explains #246"
Thanks again for pytest examples that is not (for me) overly advanced.
Wonderful explanation of argparse which I am trying to learn at the moment. And a suprisingly simple way of testing it.
At least in the beginning. But now I can start from there and learn the rest.
Do you have any examples how to test sys?
import sys
def names():
filename, first, last = sys.argv
print(f"Welcome {first} {last}.")
How do I test this?
I have been searching solutions for days on the internet. They all are too advanced for me. And not really what I am looking for.
Your solution seems to be close. For the argparse it was perfect.

[@anthonywritescode]

you can monkeypatch using the `unittest.mock` module:
```python
from unittest import mock
with mock.patch.object(sys, 'argv', ['prog', 'first', 'last']):
...
```

[@ulfsjodin7872]

@@anthonywritescode
Hello Anthony. I have tried for a week now without any success. Not all the time of course. I am just a hobby pythonista. Doing a little bit now and then
If you can give me a little bit more hints I would be glad. Challenges are great for developement. So dont give all of the answer.

[@anthonywritescode]

what are you stuck on?

[@ulfen69]

@@anthonywritescode
Do I need a @mock.patch…?
Or capsys in the def test_sys():?
And is there a readouterr() I assert something to?

[@anthonywritescode]

if you want to reliably change `sys.argv` without polluting other tests then yes use `mock.patch.object` -- I prefer the context manager over the decorator (less magical, more tightly scoped). capsys is needed if you want to test output

[@d3stinYwOw]

Looks great!
Will you plan on some tutorials how to do TDD (Test Driven Development) in practice?

[@anthonywritescode]

I did already! th-cam.com/video/JmMxU8ljiOg/w-d-xo.html

[@SC-ee5zc]

damn u r good , thanks

[@konradbeck101]

argparse throws an error if pass in an empty string
python hello.py ""
hello.py: error: the following arguments are required: person

[@anthonywritescode]

are you on windows? that should work fine I think (an empty string is a valid command line parameter)

[@konradbeck101]

@anthonywritescode Yes, I'm on windows. Ended up just using " ", so on to the next video.

[@JohnZakaria]

I find the background music a bit distracting,
Maybe I am not used to it in your videos..

[@anthonywritescode]

good news, it's gone after the first couple videos

[@OldOneX]

انته ❣️

[@tkm3ss10]

At 03:55, you can change the index to 0 to remove the index error and to 2 to get 2nd name, Jeff.

[@anthonywritescode]

that doesn't fix anything, it breaks the point of the program -- `argv[0]` is the name of the program itself

[@Walruz1000]

I noticed that in python multiple return statements seem to be accepted, whereas in all the java projects I worked on in the past the sonar builds would fail for this. What is your opinion on that?

[@anthonywritescode]

I think they're mostly fine -- there are places where multiple return statements can be confusing (and easy to miss one case or another) but as long as a type checker (such as mypy) is set up you're ~mostly guarded against being a problem. imo it's really only an issue when functions get too long and one return statement might be lost further up