function中的参数好像没有效果？

Question

I use a function that allows me to write the data of a file to a list, but I must be missing something because the parameter in my function that defines the list seems not to work, would you know what the problem is? there is my function:

filePath = path + "\ONLYIVENOTFIXED.txt"
listObj = []
i = listObj


def writeFileOnAList(pathofThefile, namelist):

    fichierIve = open(pathofThefile, "r")
    namelist = fichierIve.readlines()
    namelist = [x.strip() for x in namelist]
    i = namelist
    i = 0


writeFileOnAList(filePath, listObj)
print(listObj)

it tells me that my "namelist" settings in my function are not used, and when I call my function and try to print my list, it prints an empty list

Do you have any solutions?

Answer 1

The key issue is that Python is a pass-by-object-reference language, not pass-by-variable-reference: ie object references are passed by value. Therefore assigning to namelist in the function simply changes the value of that variable: it does not have any effect on the listobj, which still references the original list.

The most Pythonic way to fix this would be for the namelist to be returned by the function:

filePath = path + "\ONLYIVENOTFIXED.txt"

def writeFileOnAList(pathofThefile):
    with open(pathofThefile, "r") as ficiherIve:
        namelist = fichierIve.readlines()
        namelist = [x.strip() for x in namelist]
    return namelist

listObj = writeFileOnAList(filePath)

Answer 2

You do have a lot of errors in your script:

filePath = path + "\ONLYIVENOTFIXED.txt"
listObj = []

# You are declaring the variable "i" here but you are never using it
i = listObj


def writeFileOnAList(pathofThefile, namelist):

    fichierIve = open(pathofThefile, "r")

    # You are parsing your listObj as parameter (namelist) but you never use it
    # instead you are just overwriting it
    namelist = fichierIve.readlines()
    namelist = [x.strip() for x in namelist]

    # Here you are overwriting your i variable 2 times in a row and never work with it 
    # after that
    i = namelist
    i = 0


writeFileOnAList(filePath, listObj)
print(listObj)

Im not exactly sure what you want to do but this is my reworked version:

filePath = path + "\ONLYIVENOTFIXED.txt"


def writeFileOnAList(pathofThefile):
    fichierIve = open(pathofThefile, "r")
    namelist = fichierIve.readlines()
    namelist = [x.strip() for x in namelist]

    return namelist


listObj = writeFileOnAList(filePath)
print(listObj)