Why is List Variable Changing?

Question

I have a function and its work correct. It can calculate correct only send by one by. But I want to append every result in a list. The list variable is changing when every calculate. Why is changing appened list data ?

`

PLCdevice = {
    '32DI': 0,
    '16DI': 0,
    '8DI': 0
}
PLCList = []

def PLCcal(DIneed ):
    DIteklif = 12
    DItoplam = 0
    for i in range(0, 320, 8):
        DIyedek = DIteklif - DIneed
        DIoran = DIyedek / DIneed
        if DIoran > 0.26:
            break
        DIteklif = DIteklif + 8

    DIteklif = DIteklif -12
    DIteklif = DIteklif / 8

    if DIteklif / 4 >= 1 :
        x = DIteklif / 4
        PLCdevice['32DI'] = int(x)
        DIteklif = DIteklif - (int(x)*4)
    if DIteklif / 2 >= 1 :
        x = DIteklif / 2
        PLCdevice['16DI'] = int(x)
        DIteklif = DIteklif - (int(x)*2)
    if DIteklif == 1 :
        x = DIteklif / 1
        PLCdevice['8DI'] = int(x)
        DIteklif = DIteklif - (int(x)*1)
    return PLCdevice

PLCList.append(PLCcal(32))
print(PLCcal(32))
PLCList.append(PLCcal(85))
print(PLCcal(85))
PLCList.append(PLCcal(411))
print(PLCcal(411))
print(PLCList)

`

I try calculate result and store result in a list. But appened data is changing.

Asked By: Oğuzhan Korkmaz

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Source

Answer 1

Dictionaries are mutable objects, and PLCdevice is a global variable, so every time you change it in PLCcal you are changing other references too which in this case are the values you are appending.

You can simply create PLCdevice at the beginning of PLCcal

def PLCcal(DIneed ):
    PLCdevice = {
        '32DI': 0,
        '16DI': 0,
        '8DI': 0
    }
    ...

Answered By: lmiguelvargasf

Why is List Variable Changing?

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