Strange problem while using print's end argument in a loop

October 22, 2023

> python version 3.11.6
> os: Windows
> Idle: Visual studio code (Latest version)

My code looks something like this:

from time import sleep


x = [
"H",
"E",
"L",
"L",
"O"
]
for i in x:
    print(i, end="")
    sleep(.5)

when I run this expected output is:
H wait E wait L wait L wait O

but output is:
A long wait then all characters instantly.

But why?

I noticed when I don’t use end argument code works well.

""Additional info"":
also tried using sys.stdout.write() same problem.

>Solution :

When you use the end="" argument in the print function, it suppresses the newline character (\n) that print normally adds at the end of each print statement.

you can use flush=True argument in the print function, to solve this:

from time import sleep

x = [
    "H",
    "E",
    "L",
    "L",
    "O"
]

for i in x:
    print(i, end="", flush=True)
    sleep(.5)

As an alternative, you could achieve the same result by combining sys.stdout.write() and sys.stdout.flush():

import sys
from time import sleep

x = [
    "H",
    "E",
    "L",
    "L",
    "O"
]

for i in x:
    sys.stdout.write(i)
    sys.stdout.flush()  # Flush the output buffer
    sleep(.5)