Why do I get this error in Python? [migrated]

I’m making a program where if a user enters text it will convert any caps into lowercase:

def lowerChar(char):
   if ord(char) >= 65 and ord(char) <= 90:
      char = int(ord(char)) + 32
      char = (chr(char))
      return print(char)
   else:
      return print(char)

def lowerString(string):
   x = len(string) 
   for i in range(x):
       char = string[0 + i]
       lowerChar(char)
       result = ""
       result = result + lowerChar(string[i])  

string = input("type")
lowerString(string) 

The error is:

Traceback (most recent call last):
  File "C:\Python34\njn.py", line 24, in <module>
    lowerString(string)
  File "C:\Python34\njn.py", line 19, in lowerString
    result = result + lowerChar(string[i])
TypeError: Can't convert 'NoneType' object to str implicitly

Any help will be appreciated.