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My mini program takes a string from user input and adds dots between each letter and then removes these dots.

The function add_dots takes the string and adds dots. I have a separate function called remove_dots that then removes them.

Here is the code below:

def add_dots(str):
  str = ".".join(str)
  print(str)

def remove_dots(str):
  str.replace(".", "")
  print(str)

word = input("Enter a word: ")

When I call the two functions individually with

add_dots(word)
remove_dots(word)

I get the expected console output of

Enter a word: hello
h.e.l.l.o
hello

However, when I try to call

remove_dots(add_dots(word))

I get an error AttributeError: 'NoneType' object has no attribute 'replace'

I understand that this means the str variable has the value of None but I'm not sure why? Can anyone advise. Thanks

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3
  • 2
    Because your add_dots doesn't return anything, or more precisely, returning None. Commented Feb 9, 2021 at 2:37
  • 1
    "add_dots" doesn't return anything, it only prints. Commented Feb 9, 2021 at 2:38
  • "I understand that this means the str variable has the value of None but I'm not sure why?" Well, what value do you think it should have? Why should it have that value? How do you expect the program to cause that to happen? Commented Feb 9, 2021 at 2:43

4 Answers 4

Reset to default
2

This is caused because your add_dots and remove_dots functions aren't actually returning anything, they're just printing values. Thus, passing the output of add_dots to remove_dots results in the value None being passed.

Also note that using str as a variable name is generally a bad idea; using string or a more descriptive name is better practice.

Change your code to return the modified strings, like so:

def add_dots(string):
  string = ".".join(string)
  return string

def remove_dots(string):
  string = string.replace(".", "")
  return string

word = input("Enter a word: ")

And print the outputs like so:

print(add_dots(word))
print(remove_dots(word))
print(remove_dots(add_dots(word)))
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Comments

0

Your functions don't return anything. Also, the output of str.replace(".", "") is not stored. This should work.

def add_dots(str):
  return ".".join(str)

def remove_dots(str):
  return str.replace(".", "")
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Comments

0 
def add_dots(str):
    str = ".".join(str)
    print(str)
    return str

def remove_dots(str):
    str = str.replace(".", "")
    print(str)
    return str

this should fix your code.

See @Chris and @Michael Butscher comments on your post

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2 Comments

remove_dots() will return the input string in your answer.
Strings are never modified in-place, so in your answer, it needs to be reassigned.
0

When you return in something in function, You have to convert return in other datatype such as list , string. In this case, Your first function it should be

def add_dots(string):
  string = ".".join(string)
  print(string)
  return str(string)

And second function should be

 def remove_dots(string):
    string = string.replace(".", "")
    print(string)
    return str(string)

Because anything that return from function, It return "Nonetype" as default. And Nonetype no method __getitem__

ref:https://www.pythonpool.com/typeerror-nonetype-object-is-not-subscriptable/

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