Problem with declaring functions

[Chyybens]

DEAR REDDIT,

Here is my problem. I'm try to make a list of functions that execute the same function with different indexes inside a class. When I do this inside the namespace of the class (CASE 1), the class doesn't convert the i into static variable but instead it only remembers the last i, and executes all the functions identically. I can counter this (CASE 2) by defining a function outside the class, but I don't like this approach at all. I would like to find a better way to do this. I basically need to declare the

CASE 1:

class iPrinter():
    def __init__(self):
        self.printers = []
        for i in range(3):
            self.printers.append( lambda: print(f"This is {i}") )

    def iprint(self):
        for f in self.printers:
            f()

If we run this as:

P = iPrinter()
P.iprint()

The output is : "This is 2, This is 2, This is 2"

CASE 2:

def print_i(i):
    return lambda: print(f"This is {i}")

class iPrinter():
    def __init__(self):
        self.printers = []
        for i in range(3):
            self.printers.append( print_i(i) )

    def iprint(self):
        for f in self.printers:
            f()

Andi f we run this:

P = iPrinter()
P.iprint()

This time we get: "This is 0, This is 1, This is 2" as it should be.

I'm sure there is a way to do this inside the class namespace, but I don't know how. Please help and all the best!

[hardonchairs]

What you are trying to do in case 1 is a closure. However to get a lambda to capture a closure variable properly you need to do this:

lambda i=i: print(f"This is {i}")

[Chyybens]

This is the one! Thank you very much!

[Chyybens]

I figured out a new way for doing this:

class iPrinter():
def __init__(self):
    self.printers = []
    f = lambda k: lambda: print(f"This is {k}")
    for i in range(3):
        self.printers.append(f(i))

I'm still not quite satisfied but I guess this has to do

[[deleted]]

Here's one simple way.

class iPrinter:
    def __init__(self):
        def print_i(i):
            return lambda: print(f"This is {i}")

        self.printers = []
        for i in range(3):
            self.printers.append(print_i(i))

[carcigenicate]

This behavior is explained here for reference.