README.md: Add logical (IF, OR, ELSEIF, ELSE) section and examples

[mikkovedru]

README.md: Add logical (IF, OR, ELSEIF, ELSE) section and examples

It took me a long time to understand how I could manipulate the output formats in a logical way. Even the realization that it was possible at all took the longest time. I hope that improving the documentation will save a lot of time for other people.

I used practical examples, that illustrate the logic, but also introduced a lot of useful yt-dlp's opportunities as well as provided a better understanding via demonstrating surprising gotchas and important caveats.

Template

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• At least skimmed through contributing guidelines including yt-dlp coding conventions
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• Checked the code with flake8 and ran relevant tests

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What is the purpose of your pull request?

• Fix or improvement to an extractor (Make sure to add/update tests)
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Copilot Summary

🤖 Generated by Copilot at 789ba9e

Summary

📝🗝️📋

Enhance output template syntax documentation in README.md. Add more explanation, keywords, and examples to help users customize their output filenames.

If you want to download some clips
And customize your output scripts
You'll appreciate
The template update
That adds keywords, examples, and tips

Walkthrough

• Clarify the meaning of s and d format types in output template syntax (link)
• Add logical keywords (IF, OR, ELSE) to output template syntax for more intuitive and readable expressions (link)
• Provide examples of using logical output template syntax in different scenarios in README.md (link)

[bashonly]

All of the pseudocode in the "logical code examples" section would cause confusion for most users, IMO

[coletdjnz]

All of the pseudocode in the "logical code examples" section would cause confusion for most users, IMO

Maybe this would be better off in the wiki?

[mikkovedru]

@bashonly

All of the pseudocode in the "logical code examples" section would cause confusion for most users, IMO

I disagree.

When learning a new programming/formatting language there are basic cornerstones that must be and are practically taught for beginners:

1. How to print (Hello World!), how to modify the output.
2. Variables and how to work with them (numbers, strings; how to modify them)
3. How to control the flow logic of the program (how to check if a variable has a certain value and what to do depending on the result)

These are the basic things that every person (wanting to utilize the language) needs to know. And if the person already has programming experience, it is the first thing he is seeking for in the documentation.

This is the wiki for Python:

This is the content of the basic 4h video course on Python:

Control of the flow is a critical part of learning the language.

In yt-dlp's "output language" the basic case of 1st is handled automatically. The more complex cases are explained, but the explanation could be better. The 2nd is in a similar situation - whatever is applicable to yt-dlp - it is explained, but the easiness of explanation could definitely be improved. The third is partly explained, partly not; but even when it is formally presented, the explanations/order/language/terminology are very difficult to get through.

My PR is drastically improving the 3rd aspect, while also making the 1st and 2nd better by showing useful examples that the reader might actually want to get.

My pseudocode would cause confusion to people who are not in a position to receive this information. But they would get even less from the current explanatory list. But for people who seek this information and are theoretically capable of receiving it, the new section and examples would make it so much easier and better. Remember that I am not suggesting removing the current list and replacing it with my section. I am simply suggesting adding the new section in order to make the syntax much more approachable and easer/faster to understand.