CODEWITHSUNDEEP
pythonfunctionreferencelvalue
Hanfei Sun
Hanfei Sun

Reputation: 47071

Return lvalue from function in Python?

I tried to write a function which can return a reference of an element for assginment, the sample code looks like this (Python3) :

row_a = ["rowname","items1","items2"]
def rowname(row):
    return row[0]
rowname(row_a) = "another_rowname"

However, it will not work because the intepreter complains like:

SyntaxError: can't assign to function call

Does anyone have idea about how to implement a function like this?

Upvotes: 1

Views: 822

Answers (3)

Hanfei Sun
Hanfei Sun

Reputation: 47071

Just found a ugly way .. Thougn setattr needed..

row_a = ["rowname","items"]
def rowname(row):
    class inner:
        def __init__(self):
            self.__dict__["to_l"] = None
        def __setattr__(self,name,value):
            row[0] = value
    return inner()
rowname(row_a).to_l = 20
print(row_a)

Upvotes: 0

sada haruna
sada haruna

Reputation: 33

Return value from a function can't be used as a variable. You can rather assign the return value to a variable. Your list definition sees like you wanted to create a dictionary. Why not sat exactly what you expected to get?

Upvotes: 0

Matt Ball
Matt Ball

Reputation: 359966

There isn't a Pythonic way of doing this. You cannot return an lvalue in Python – Python isn't C++! If you just want use a function to to set the value of the first element of a list, just do that:

row_a = ["rowname","items1","items2"]
def set_rowname(row, value):
    row[1] = value
set_rowname(row_a, "another_rowname")

Upvotes: 1

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