Why does a append() operation in my python code evaluate to None?

Question

so I was writing a pig latin translator program, and I ran into trouble, when trying to append the first letter of each word to the end of the word. I debugged the code, and I found that the line "list=listEnd.append(firstLetter)" (in bold below) was evaluating to None, which caused the next line, "list=list.append('ay')" to crash. Can anybody tell me why this is happening?

The error message is: Traceback (most recent call last): File "C:\Python34\pigLatinTranslator.py", line 33, in list=listEnd.append(firstLetter).append('ay') AttributeError: 'NoneType' object has no attribute 'append'

Thanks!!

def getSentence():
    print('Enter a sentence you would like to translate to pig Latin(letters and           spaces only)')
    sentence=input()
    return sentence

def isStartsWithConsonant(word):
    for i in 'bcdfghjklmnpqrstvwxyz':
        if word.startswith(i):
            return True

while True:
    sentence=getSentence()
    #if isValidSentence(sentence):
    sentenceList=sentence.split()
    listLists=[]
    for w in sentenceList[:]:
        wList=[]
        for l in w:
            wList.append(l)
        listLists.append(wList)

    for list in listLists:
        if isStartsWithConsonant(list[0]):
            listEnd=list[1:]
            firstLetter=list[0]
            list=listEnd.append(firstLetter).append('ay')

        else:
            listEnd=list[1:]
            firstLetter=list[0]
            list=listEnd.append(firstLetter)
            list.append('way')
    translatedSentence=''
    for list in listLists:
        for l in list:
            translatedSentence.append(l)
        translatedSentence.append(' ')
    print('Your sentence translated to pig Latin is:'+translatedSentence)
    print('Do you want to translate another sentence?')
    if not input().startswith(y):
        break

`append` just modifies the list, it doesn't return anything. — Barmar, Sep 03 '15 at 19:36
sorry, for some reason the line isn't coming out in bold! It's the 14th line down from the "while True" statement! — Everett Shen, Sep 03 '15 at 19:36
@Barmar Sorry about that! The while True block is indented in my program — Everett Shen, Sep 03 '15 at 19:39
Can you indent it in the question, please? I'd do it for you, but I can't tell where the end of the loop should be. Correct indentation is crucial in Python. — Barmar, Sep 03 '15 at 19:42

score 1 · Accepted Answer · answered Sep 03 '15 at 19:40

1

append returns None in python. You can either do:

listEnd.append(firstLetter)
list = listEnd

or

list = listEnd + [firstLetter]

answered Sep 03 '15 at 19:40

Aaron Yuan

26
3

Thanks! helped a lot! – Everett Shen Sep 03 '15 at 20:28

Why does a append() operation in my python code evaluate to None?

1 Answers1