CODEWITHSUNDEEP
pythonasciimsvcrt
Ashiataka
Ashiataka

Reputation: 97

How to capture special keys for python console application

Python 2.7

I'm trying to capture key presses in an application I'm writing using the getch() function in the msvcrt module. Some are easy, enter is 13, backspace is 8, .> is 46 etc. Some keys, such as Home, I can't work out.

From the docstring for getch():

"If the pressed key was a special function key, this will return ‘000’ or ‘xe0’; the next call will return the keycode."

I've tried testing for a return value of '000' or 'xe0' but this is not returned. What happens is I get 224 returned and on the next call of getch() I get another code, so for Home it's 71. Other special keys behave this way too, End is 224 79, Insert is 224 82, Page Up is 224 73 etc. I can't explain this behaviour; I've tried seeing if adding the two values together and then taking off a power of two helps (i.e. 224 + 73 - 256) but it doesn't produce anything useful.

Does anyone understand this behaviour and/or does anyone have any advice about how to capture these keys (I didn't want to hard code the 224 + x pattern values as I'm not confident these are consistent with other users)?

Thank you.

EDIT: code if anyone wants to try it out

import msvcrt

while True:
    key = msvcrt.getch()
    print ord(key)

Upvotes: 0

Views: 1406

Answers (1)

Lukas Graf
Lukas Graf

Reputation: 32650

The mentioned value returned by getch() is not 'xe0', it's '\xe0' - note the backslash indicating an escape sequence. 224 is just the decimal value of that byte:

ord('\xe0') == 224

So in your case, this should work:

while True:
    key = msvcrt.getch()
    if key in ('\000', '\xe0'):
        # special key, handle accordingly
        # ...

Upvotes: 1

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