Variable Scope

Question

Im trying to add up all the digits in a number. Im not so sure if my for loop is the most efficient way of doing this. Im creating a new list of the numbers that i converted to an int in another variable and printing out the sum of that list because i cant return the sum of the variable because its only inside the for loop. Is there a better way of doing this?

https://code.sololearn.com/cgXECPuAt6S2/?ref=app

Answer 1

You could also use the map() function to make the string digits integers:
print(sum(map(int, list("123"))))

Answer 2

G B Okay so map requires a function and is applied to each element and then map is returning an iterable and sum is going through that iterable.

Answer 3

map() is basically: "Apply this function to each element of my iterable", here int() is applied to each character of the string.

Answer 4

2 Things to refine.
1. The map function applies the given function to every Element in the given iterable. All the results are then packend into an iterable again, which will be returned. So map itself evaluates to an iterable.
2. In python there actually is no such concept as type casting. Python is not strictly typed, so a variable Can change its type during runtime. What the int function does is, it Creates a new int object and Returns it.
So Yes, int() is a function (method) - more specifically the it is the "constructor" method of class int.

Answer 5

G B Thanks

Answer 6

Junior exactly.

Answer 7

you do not have to create a new distinct list object, But you could use a list comprehension as in add_digits2:

from time import perf_counter
import numpy as np

def add_digits(digits):
store_numbers = list(digits)
new_lst = []
for item in store_numbers:
conv_number = int(item)
new_lst.append(conv_number)
return sum(new_lst)

def add_digits2(digits):
store_numbers = list(digits)
return sum([int(num) for num in store_numbers] )

runtime = []
for _ in range(1000):
t0 = perf_counter()
result = add_digits("123")
runtime.append(perf_counter() - t0)
print(f" {result}, {np.mean(runtime)}")

runtime = []
for _ in range(1000):
t0 = perf_counter()
result = add_digits2("123")
runtime.append(perf_counter() - t0)
print(f" {result}, {np.mean(runtime)}")

This may only be a tiny bit more efficient though...

Answer 8

Lisa :
true, this makes it much more effective 👍

Answer 9

Lisa Thanks, i will definently see more about map

Answer 10

Lisa I do have one question. okay so maps require a function right, so correct me if im wrong but int isnt a function. Is it converting the number to an ingeter like type casting?

Answer 11

Oh wait im getting ahead of myself, okay so I got rid of list because map take iterables and strings are iterables but then im casting it as an int and ints are not iterables? So what is exactly happeninng here?

Answer 12

Lisa So how is my sum working then because its an int, sun only takes iterables and integers are iterablw unless you put it in like a list or something

Answer 13

Lisa So is map like how list work? it stores that number in it? and go goes through it amd finds the sum?