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in python, how do i check if an user boolean input is true or false (lemmy.ml)

submitted 1 year ago by jackpot@lemmy.ml to c/asklemmy@lemmy.ml

25 comments fedilink hide all child comments

to my knowledge, if you input any text it will return true and if you input nothing it will return false. if it's possible without if statements, how do i check if they inputted 'True' or 'False (/ '1' or '0') when im doing 'bool(input("Input True or False ")'.

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[–] originalfrozenbanana@lemm.ee 10 points 1 year ago* (last edited 1 year ago) (1 children)

Without if statements?

Apologies typing on my phone

def input_checker(input_str):

input_str = input_str.lower()

validation_dict = {“true”: “they input true”,
                               “false”: “they input false”}

return validation_dict.get(input_str, “They input something else”)

You are comparing the content of strings, not their truth value. A string is true if it’s not empty and false if it is. The string “True” is no closer to the bool True than the string “Oranges” is.

What you are looking for is input validation. Check the content of what they wrote and respond accordingly.

[–] jackpot@lemmy.ml 2 points 1 year ago (4 children)

why is my input being seen as a string in the firsr place if i typecasted the variable as a boolean? how do i make the input itself a bool (rather than the variable?)

[–] originalfrozenbanana@lemm.ee 12 points 1 year ago* (last edited 1 year ago) (1 children)

User inputs are strings, which can be anything. You are hoping they input True or false but what if they input tRUe or FALSE77 or Hunter4 or jgidqopqncb uriwnsvsveyqiaoNcbtjwnak? bool(“tRUe”) doesn’t evaluate to True or False in the way you think it does.

If you want to convert user input to a bool use a lookup dict with some validation rules (like lower casing input text) to sanitize the input. I cannot emphasize this enough - never trust user input.

[–] TechieDamien@lemmy.ml 1 points 1 year ago

Always trust user input'); DROP TABLE users;

[–] Brotherly@lemm.ee 5 points 1 year ago* (last edited 1 year ago)

Worth remembering that python uses the concepts of truthy and falsey. Empty string ("") is falsey. Any other string ("true", "false", "0", etc.) Is truthy. All bool(str) does is evaluate whether str is truthy or falsey. It does not evaluate what str actually is.

So bool(input("Input True or False ") will return False is the user input is empty and True otherwise.