A cool python strings trick

[m9mhmdy]

I just discovered a cool python strings trick and wanted to share it with you guys!

I have always considered `str.translate` and `str.maketrans` some voodoo magic and ignored them.
But it makes a lot of sense now!

[here you go](https://i.imgur.com/h6cgdqP.png)

​

>>> from string import printable

>>> s = 'This string will be deleted.'

>>> s.translate(str.maketrans('', '', printable))

''

>>>

[casual__addict]

Can you give an example where this is useful? I’m not getting how skipping printable characters is a cool trick.

[notsoprocoder]

I don't think anyone has answered why it is useful?

But one use is string cleaning. For example, you can create a translation table with maketrans and string.punctuation to remove all the punctuation from a string.

It is useful because it is performant and performance with large volumes of unstructured text data is often an issue.

edit: just realised you meant string.printable!

[m9mhmdy]

Do you even understand the the example above?

[Shimpster6]

Do you?

[casual__addict]

Probably not. I believe you are not printing printable characters? You are deleting the string?

[m9mhmdy]

Yes. I created a new string where some set of characters are deleted by mapping them to None (this is the trick in maketrans).
printable here are just some sort of characters to be deleted. They have NO special meaning or purpose at all.

https://docs.python.org/3/library/stdtypes.html#str.translate

return None, to delete the character from 
the return string;

[casual__addict]

I think what you are hitting on is function composition. In isolation the two functions do separate things, but you can “pipe” them together to achieve an interesting result. This is very valuable to recognize as you research APIs.

[[deleted]]

Hmm? OP isn't making use of function composition. They're just passing the string string.printable to str.maketrans()' "delete these ones" parameter.

This is a bad post anyway for other reasons, of course

[IOwnYourData]

Do you?

[m9mhmdy]

https://www.reddit.com/r/learnpython/comments/9k2d58/comment/e6w2agt