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, Apr 04 '20 at 09:14
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, Apr 04 '20 at 09:15
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, Apr 04 '20 at 09:24
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, Apr 06 '20 at 13:52
It seems you are looking for the "walrus operator". See https://stackoverflow.com/questions/50297704/syntax-and-assignment-expressions-what-and-why — mkrieger1, Apr 06 '20 at 13:55

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

1

There are at least two ways:

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

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

edited Jun 20 '20 at 09:12

Community

answered Apr 04 '20 at 09:15

L3viathan

Which one is faster? it would be nice if they add such keyword to make it even nicer. – DragonKnight Apr 06 '20 at 13:53

score 1 · Answer 2 · answered Apr 04 '20 at 09:21

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.

answered Apr 04 '20 at 09:21

mkrieger1

It is not about the str() method. That is just an example. How can I make that operation inside for loop? – DragonKnight Apr 06 '20 at 13:50

2 Answers2