Question

I can’t convert a string to an integer correctly with the code below.

I take lang input as a string. I want to accept any input, because if I restrict the input to integers, then any letter entered by the user will cause an error.

This code:

lang=[]
def chooseLang():
    global lang
    while lang !='1' and lang != '2':
        print ('Select (1 or 2):')
        lang=input()
    return lang

def convertStr(lang):
    ret=int(lang)
    return ret   
#-----------------------Program-----------------------
chooseLang()
convertStr(lang)

c=2+lang
print (c)

… causes this error:

in <module> c=2+lang
TypeError: unsupported operand type(s) for +: 'int' and 'str'

Trying do everything in one function has the same effect:

lang=[]    
def chooseLang():
    global lang
    while lang !='1' and lang != '2':
        print ('Select (1 or 2):')
        lang=input()
    return lang
    ret=int(lang)

chooseLang()
c=2+lang
print (c)

What am I doing wrong?

Answer 1

You forgot to use the returned value from convertStr() function in the first example:

lang = convertStr(lang)

In your second example ret = int(lang) is unreachable due to return lang before it.

Example

def choose_lang():
    lang = None # NOTE: this `lang` has nothing to do with the global `lang`
    while True: 
        try:
            lang = int(input("select (1 or 2)"))
        except ValueError:
            pass
        if lang not in [1, 2]:
            print("\ntry again")
        else:
            break
    return lang

lang = choose_lang()
c = 2 + lang
print(c)