in python, how do i check if an user boolean input is true or false
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 ")'.
Post your code to Stack overflow and make the title of the post something like "found efficient way to check if user input boolean value"
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.
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?)
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.
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.
You can use eval(input). It converts string to whatever the actual content is.
Use argparse instead of input
it's a good thing, but for a very simple script used to learn stuff it's way overcomplicated
input("question").lower().startswith("t") is my go to. More fault tolerant and gets the job done
y/n/1/0 ?
Text input by a user is almost always a string, because the user presses 0 or more keys on their keyboard before hitting enter.
Without validation, we have no way to know that the user typed - did they type “1” or “True”, or did they embrace chaos and type in “Batman”? Unless we check, we can’t be sure.
We can assume, but then we have to accept that our program will have what we call “undefined behaviour” if our assumption is incorrect - which is definitely not good. In the best case scenario, your code harmlessly crashes. In the worst case scenario, your code is being used by the Pentagon for some reason and just started global thermonuclear war, which ideally should be avoided.
There are ways around this. For example, we could listen for individual keystrokes and only accept the inputs if they meet our criteria - if the user presses the 1 key, that’s true, if they press 0, that’s false, any other key is ignored, for example.
But the best thing to do, in my humble opinion, is to accept a string input and then check what the user entered. In most cases, “True” or “False” aren’t usually what we want, unless you’re writing some sort of true or false guessing game or something. Most cases where we want a Boolean input from a user, it’s a yes/no kind of thing. “Would you like to continue?” or “Shall we start global thermonuclear war? y/N”
So you’re better off just embracing the string, and using that to determine behaviour, rather than a Boolean directly. For example, something along the lines of :
if user input is “y” then launch nukes
else if user input is “n” send fruit basket
else print “input invalid”`
As others mentioned in the thread, it may be wise to convert the input to lowercase - just in case the user enters Y or y. Personally I wouldn’t go so far as to take the first letter as the answer, in case the user enters “you must be joking!” for example :-)
Just use 'strtobool' from distutils to parse str as bool much better than reinventing the wheel https://docs.python.org/3.11/distutils/apiref.html#distutils.util.strtobool
edit: ok it uses if internally so without if you could do it with match statement
I'm a little rusty, but can't you do it with a '?'
something like,
var ? print("true") : print("false")
I have to imagine the ternary operator would still count as an if statement in spirit
I think you're thinking of JavaScript, not Python. The closest thing Python has to a ternary operator is foo if condition else bar.
You might be right actually.
input("Input True or False") == "True"Will work but this strikes me as a likely example of an XY problem. What are you actually trying to achieve?