Capital letters in text input

I have a trial where participants are asked to enter a string of text. Special characters are defined as in the chunk of code below.
My problem is that I can’t seem to enter capital letters. Does anyone know how to go about doing this?

shift_flag = False
for key in event.getKeys():
        if key in ['escape']: 
            core.quit()
        elif key in ['return']:
            if len(captured_string) > 1:
                subject_response_finished=True
                final_response=captured_string
                continueRoutine=False
        elif key in ['delete','backspace']:
            captured_string = captured_string[:-1] 
        elif key in ['space']:
            captured_string = captured_string+' '
        elif key in ['period']:
            captured_string = captured_string+'.'
        else: 
            captured_string = captured_string+key

Hi jmmb, maybe you can try to add this:
elif key in [‘lshift’, ‘rshift’]:
shift_flag = True

@Xiaotong is correct, you need to explicitly handle the shift keys, there is some more complete code here:

How to compare inputText to CorAns

But note that it is horribly old-fashioned and will only work on ASCII-style text (ie wouldn’t handle any special characters with accents, etc).

Thanks, Xiaotong and Michael. I solved it like this shortly after posting (sorry for not updating quicker), so essentially like Xiaotong suggests:

    try:
   	shift_flag
    except NameError:
	shift_flag = False
    
    for key in event.getKeys():
        if key in ['escape']: 
            core.quit()
	elif key in ['lshift','rshift']:
	    shift_flag=True
	    pass
        elif key in ['return']:
            if len(captured_string) > 1:
                subject_response_finished=True
                final_response=captured_string
                continueRoutine=False
        elif key in ['delete','backspace']:
            captured_string = captured_string[:-1] 
        elif key in ['space']:
            captured_string = captured_string+' '
        elif key in ['period']:
            captured_string = captured_string+'.'
	elif shift_flag == True:
		captured_string = captured_string+key.upper()
		shift_flag = False
        else:
	    captured_string = captured_string+key

Michael, could you explain which part is old-fashioned and why? (the way of handling capitals, or the whole way of handling special characters?) Special characters with umlauts work ok with this (by giving e.g. ü as input when the left bracket is pressed).

The code might rely on old-style approaches with text being assumed to be ASCII rather than Unicode. But if it works for you in practice, it doesn’t matter if it’s old-fashioned. Go for it.