Can't seem to split a string in Python

Question

I'm trying to split a string at its commas in Python at the moment and I'm getting the error main() missing 1 required positional argument: 'self' This is what I have as of right now.

def main(self):
    last_letters('Ani,Trevor,Karen,Jasmine,Ryan')

def last_letters(self):
    last_letters1 = last_letters.split(",")
if __name__ == '__main__':
    main()

EDIT: After I remove self from the def, I am still left with this error--

`Traceback (most recent call last):
  File "/home/main.py", line 13, in <module>
    main()
  File "/home/main.py", line 2, in main
    last_letters('Ani,Trevor,Karen,Jasmine,Ryan')
TypeError: last_letters() takes 0 positional arguments but 1 was given

`

Answer 1

If you declare that a function takes a positional argument, then you must supply that argument when calling the function.

As it is, your main() function does not require any argument so just change it to:

def main():
    last_letters('Ani,Trevor,Karen,Jasmine,Ryan')

Also, the argument name self is by convention used as a reference to an object instance within the object itself. You find it as the first argument to a method (a function that is bound to an instance of an object), whereas you are using standalone function.

The argument to last_letters() is the string 'Ani,Trevor,Karen,Jasmine,Ryan' when that function is called in main(). last_letters() does require the argument, but for the aforementioned reasons it should not be named self. You could just call it s or something descriptive of its value.

Finally the line last_letters1 = last_letters.split(",") won't work. You need to call split() on a string instance, like this:

def last_letters(text):
    names = text.split(",")
    # do something with names...
    # return a list containing the last letter of each name
    return [name[-1] for name in names]

Answer 2

I suggest you write code first without functions as this is a small program and once it's running, slowly convert into functions and this helps in understanding it without functions.

if __name__ == '__main__':
    last_letters="Ani,Trevor,Karen,Jasmine,Ryan"
    last_letters1 = last_letters.split(",")
    print(last_letters1)

The mistake you did is you're trying to pass str/word but you didn't specify that in the function (just give a name so that value you passed will be stored in it)

def main():
    last_letters('Ani,Trevor,Karen,Jasmine,Ryan')

def last_letters(word):
    last_letters1 = word.split(",")
    print(last_letters1)

if __name__ == '__main__':
    main()

Exactly your code updated

def main():
    last_letters('Ani,Trevor,Karen,Jasmine,Ryan')

def last_letters(last_letters):
    last_letters1 = last_letters.split(",")
    print(last_letters1) # to print data
if __name__ == '__main__':
    main()

Answer 3

There's a number of issues:

• You call main() in and appropriate way, but as you can tell from the call main(), it doesn't need a parameter, so instead of declaring it with self as a parameter, it could just be:

def main():
    last_letters('Ani,Trevor,Karen,Jasmine,Ryan')

• Similarly, last_letters doesn't need self either. Typically, you only see self as a parameter in methods on a class, but these are just functions by themselves (and even for a class, the parameter doesn't need to be called self, it's just a convention). However, you do need to pass a text to last_letters, so it makes sense to define a parameter like text:

def last_letters(text):
    return text.split(",")

• Also note that I changed the code of the function to return the result of the split, this ensures that the result is available wherever the function was called, if you do something with it, like capture it in a variable, or print it. Let's print it from main():

def main():
    print(last_letters('Ani,Trevor,Karen,Jasmine,Ryan'))

• Since your function is called last_letters, you probably just want the last letters:

def last_letters(text):
    return [word[-1] for word in text.split(",")]

So, the result is then:

def main():
    print(last_letters('Ani,Trevor,Karen,Jasmine,Ryan'))


def last_letters(text):
    return [word[-1] for word in text.split(",")]


if __name__ == '__main__':
    main()

And the output:

['i', 'r', 'n', 'e', 'n']