So I needed to define a function that receives a list containing letters and returns a new list with all the positions of a given letter, e.g. lst = ['a', 'b', 'c'] if letter = 'a' then [0]. In my code I get
res=res.append(finallist)
AttributeError: 'NoneType' object has no attribute 'append'
What did I do wrong?
def searchlist(lst,letter):
res=[]
for i in range(len(lst)):
finallist=lst.index(letter)
res=res.append(finallist)
return res
You should change res=res.append(finallist) into res.append(finallist)
Because res.append(finallist) will not return a 'list' object, but just the success of that line of code, which is a 'NoneType' object. (actually it returns nothing.)
Now your code will look like this:
def searchlist(lst, letter):
res = []
for i in range(len(lst)):
finallist = lst.index(letter)
res.append(finallist)
return res
However, even though you run this code, your program will not give you a result what you want, e.g. lst=['a', 'b', 'c'] if letter='a' then [0, 0, 0].
You'd better use the code below to get a result what you want.
def searchlist(lst, letter):
res = []
for i, element in enumerate(lst):
if element == letter:
res.append(i)
return res
test_result = searchlist(['a', 'b', 'c', 'a'], 'a')
print(test_result)
Or you can make your code much more simple and cooler (which is preferable) by this way:
def searchlist(lst, letter):
return [i for i, element in enumerate(lst) if element == letter]
test_result = searchlist(['a', 'b', 'c', 'a'], 'a')
print(test_result)
We call this technique as "list comprehension"
I got this idea from https://stackoverflow.com/a/16685428/8423105
Good luck.
As rivamarco said in the comments you just have to remove res = from your code, because when you append an element to a list you're not making an assignment.
