Python lambda function in a list gives unexpected result-CodePudding

So I'm trying to make a list where a lambda functions are the elements of the list. The lambda function calls another function which I pass an argument to. The problem is that lambda function only 'saves' the last value for all other items in the list. See below

The question is what should I do to get the desired result?

Edit: The stated problem is simplified. I have to use lambda for the solution

This is the code I'm trying to understand the problem:

def f(B):
    print(B)
A = [lambda: f(a) for a in ["foo", "faz", "baz"]]
for a in A:
    a()

Desired result:

foo
faz
baz

Real result:

baz
baz
baz

CodePudding user response：

if you need to create an array of function calls you can achieve what you are trying to do with the following:

def f(x):
     def g():
         print(x)
     return g

A = [f(a) for a in ["foo", "faz", "baz"]]

for a in A:
    a()

output

foo
faz
baz

CodePudding user response：

While lambda accesses the context it's defined in, a for loop doesn#t create a new context each time it runs. That would be too inefficient.

Thus, by the time your code actually calls the lambda functions that context has ended and a contains the last value the loop assigned to it.

Correct code:

def f(B):
    print(B)
A = ["foo", "faz", "baz"]
for a in A:
    f(a)

If this answer is not sufficient, please clarify why do you need that lambda in the first place.

CodePudding user response：

For loop in lambda saves last item of list so its better to write it way out lambda like this:

def b():
    A = ["foo","faz","baz"]
    For a in A: 
         Print(a)

and output is:

foo
faz
baz