How to convert values in place in a python for loop?

Question

In this simple python example:

arr = [1,2,3,4,5]
for n in arr: 
    s = str(n)
    print(s)

What I want to write is a code somehow similar to [str(n) for n in arr] but in the following format:

arr = [1,2,3,4,5]
for str(n) as s in arr: 
    print(s)

I basically want to include s=str(s) inside for statement. Is the any handy way to do so in python?

What result to you expect exactly ? The list comprehension is a way to store elements not print them. Just do for n in arr: print(n) no need to pass to str — azro
– azro, Commented Apr 4, 2020 at 9:14
The first example is fine, but you could just use print(n) directly. The second example with the list comprehension is also just fine. The third example doesn’t make sense, though. — mkrieger1
– mkrieger1, Commented Apr 4, 2020 at 9:15
Can you clarify what your goal is? Do you want to convert the list in place, convert the element in the for loop, or just print the values as strings? — MisterMiyagi
– MisterMiyagi, Commented Apr 4, 2020 at 9:24
Your desired format is very obviously a syntax error. Just to be clear: You want to remove the single line s = str(s), and still want s to be a str regardless of its initial type? — MisterMiyagi
– MisterMiyagi, Commented Apr 6, 2020 at 13:52
It seems you are looking for the "walrus operator". See stackoverflow.com/questions/50297704/… — mkrieger1
– mkrieger1, Commented Apr 6, 2020 at 13:55

Community · Accepted Answer · 2020-06-20 09:12:55Z

2

There are at least two ways:

`map:`

arr = [1,2,3,4,5]
for s in map(str, arr): 
    print(s)

generator comprehensions:

arr = [1,2,3,4,5]
for s in (str(n) for n in arr):
    print(s)

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Apr 4, 2020 at 9:15

L3viathan

27.5k2 gold badges63 silver badges84 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

DragonKnight Over a year ago

Which one is faster? it would be nice if they add such keyword to make it even nicer.

mkrieger1 · Accepted Answer · 2020-04-04 09:21:30Z

1

You don't need to use str at all. The print function converts its arguments to strings automatically.

So you can simply use:

for n in arr:
    print(n)

no matter what n is.

Reference: https://docs.python.org/3/library/functions.html#print

answered Apr 4, 2020 at 9:21

mkrieger1

24.2k7 gold badges68 silver badges84 bronze badges

1 Comment

DragonKnight Over a year ago

It is not about the str() method. That is just an example. How can I make that operation inside for loop?

Collectives™ on Stack Overflow

How to convert values in place in a python for loop?

2 Answers 2

`map:`

generator comprehensions:

1 Comment

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

map:

generator comprehensions:

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related

`map:`