issue with recursive method and global variable in python 3

In python, to keep track of variables that need to exist during the recursion, you use an argument with a default value.

def palindromeMethod(theWord, num=0):
                       # here ^
    length = len(theWord)
    if(theWord[num]==theWord[length-num-1]):
        if(num>=length-1):
            return True
        return palindromeMethod(theWord, num+1)
                          # pass it here ^
    else:
        return False

if palindromeMethod('aabbccbbaa'):
   # don't need to pass it here ^
    print('its a palindrome')

I moved the print outside the function and fixed some off-by-one errors.

Variables inside the functions has a local scope ,thus you need to initial the num inside the function ! But as you have a recursion function here you couldn't specify a num=0 in your function .

So my suggestion for such problem is :

• pass the num as an argument to your function :

def palindromeMethod(theWord,num=0):
   length = len(theWord)
   if(theWord[num]==theWord[length-num]):
       if(num>length):
            print(theWord, "is a palindrome")
            return True
       num = num+1
       return palindromeMethod(theWord,num)
   else:
       return False

No need for indices or lengths

def pal(w):
    if w == "": return True
    if w[0] != w[-1]: return False
    return pal(w[1:-1])

but you may have been requested to use them...

Edit

Following a comment of the OP, that effectively narrows the spectrum of possible responses, here it is a look ma, no slices version of the above.

def pal(w, l=0, n=0):

    # in production use: l = l if l else len(w)
    if l ==0:
        l = len(w)
        print(("0123456789"*3)[:l])
        print(w)

    print(n, l-n-1, w[n], w[l-n-1])
    if w[n] != w[l-n-1]: return False
    if n+1 >= l-n-2: return True
    return pal(w,l,n+1)

# a bit of testing
for word in ('aabbcbbaa', 'aabbccbbaa', 'aabbccbaa', 'aabbcdbbaa',
             'saippuakivikauppias'):
    print('Is the word "%s" palindrome? %s.' % (word, pal(word)))

The print expressions were used to show the work in progress of the function, the OP may want to remove them, as they were not requested (NB: w/o prints etc it's 5 LOC).

Output of testing

012345678
aabbcbbaa
0 8 a a
1 7 a a
2 6 b b
3 5 b b
Is the word "aabbcbbaa" palindrome? True.
0123456789
aabbccbbaa
0 9 a a
1 8 a a
2 7 b b
3 6 b b
4 5 c c
Is the word "aabbccbbaa" palindrome? True.
012345678
aabbccbaa
0 8 a a
1 7 a a
2 6 b b
3 5 b c
Is the word "aabbccbaa" palindrome? False.
0123456789
aabbcdbbaa
0 9 a a
1 8 a a
2 7 b b
3 6 b b
4 5 c d
Is the word "aabbcdbbaa" palindrome? False.
0123456789012345678
saippuakivikauppias
0 18 s s
1 17 a a
2 16 i i
3 15 p p
4 14 p p
5 13 u u
6 12 a a
7 11 k k
8 10 i i
Is the word "saippuakivikauppias" palindrome? True.

Final fireworks: the much expected one-liner

def pal(w): return 1 if w=="" else 0 if w[0]!=w[-1] else pal(w[1:-1])

ok I played around with it and came up with this, which works with no errors:

aWord = input("enter the word now")
num = 0

def palindromeMethod(theWord, num):
    length = len(theWord)


    if(theWord[num]==theWord[length-(1+num)]):
        if(num>=length-1):
            print("its a palindrome")
            return True
        num = num+1
        palindromeMethod(theWord,num)
    else:
        return False

palindromeMethod(aWord,0)

however i am not 100% certain why this works. I'm guessing that when i say 'return True' it breaks out of the outer if block and doesn't execute the next two lines in the if block (num = num+1 and palindromeMethod(theWord,num).... is this correct?