python say isalpha() is not defined despite it being built in (I think)

Question

i am running a program that takes a list of numbers and letters, and separates the numbers into a sperate list and printing that list, but every time i run the code it says that isalpha is not defined.

yes = []
item=[1,7,-10,34,2,"a",-8]
for things in item:
    if isalpha() ==True:
        continue
    else:
        yes.append
        print(yes)

Answer 1

isalpha() is a method for the str class which returns True if all the characters inside a string are letters and False if that's not the case. Example:

>>> MyString = "fwUBCEFèfewf"
>>> MyString.isalpha()
True
>>> MyOtherString = "f13bbG"
>>> MyOtherString.isalpha()
False

In order to separate all the letters and numbers inside the item array you need to rewrite your code like this:

letters = []
numbers = []

item=[1,7,-10,34,2,"a",-8]
for things in item:
    if str(things).isalpha():
        letters.append(things)
    else:
        numbers.append(things)

print(letters)
print(numbers)

# output:
# ['a']
# [1, 7, -10, 34, 2, -8]

You will have to do str(things) inside the conditions because the isalpha() is only a function you can use on strings and not integers. If you don't add this you will get an error saying AttributeError: 'int' object has no attribute 'isalpha'.

You could also do this if you use the isinstance() function to check wether things is a string or not. You would do it like this:

letters = []
numbers = []

item=[1,7,-10,34,2,"a",-8]
for things in item:
    if isinstance(things, str) and things.isalpha():
        letters.append(things)
    else:
        numbers.append(things)

print(letters)
print(numbers)

# output:
# ['a']
# [1, 7, -10, 34, 2, -8]

Since the letters can only be strings you can check if the things is of type str with the isinstance() function. Here two conditions have to be True.

I hope that I could help you :)

Answer 2

.isalpha is a method not a function ^{(see this tutorial to learn more about the difference)}, so it cannot be called by name. I think you want

    if str(things).isalpha(): continue

or

    if isinstance(things, str) and things.isalpha(): 
        continue

Also, the else is not necessary after continue, so you can follow with yes.append(things) ^{(not just yes.append)}:

yes = []
item=[1,7,-10,34,2,"a",-8]
for things in item:
    if isinstance(things, str) and things.isalpha(): 
        continue
    yes.append(things)
    print(yes)

(But why are you printing yes [potentially on repeat] inside the loop instead of after the loop?)

---

Alternately you could just use list comprehension ^{(view output)}

item=[1,7,-10,34,2,"a",-8]
yes = [i for i in item if not (isinstance(i, str) and i.isalpha())] 
print(*yes, sep='\n')