Wy can't Powershell display a string when i use stdout in Python?

Question

It runs fine in VS Code, but in powershell it does prompt user input but without displaying the string in "stdout". Here is the sample piece of code:

import sys


def get_int():
    sys.stdout.write("Enter number(s). ")
    return map(int, sys.stdin.readline().strip().split())


def get_float():
    sys.stdout.write("Enter number(s). ")
    return map(float, sys.stdin.readline().strip().split())


def get_list_of_int():
    sys.stdout.write("Enter numbers followed by space. ")
    return list(map(int, sys.stdin.readline().strip().split()))


def get_string():
    sys.stdout.write("Enter string. ")
    return sys.stdin.readline().strip()


a, b, c, d = get_int()
e, f, g = get_float()
arr = get_list_of_int()
str = get_string()

0x5961736972: can you please provide a source backing your statment? AFAIK input() doesn't slow your script. — Pedro Lobito
– Pedro Lobito, Commented Jun 13, 2020 at 14:22
The question that you linked is unrelated to input slowering your script, it actually talks about output. I won't post any further comments here, but I definitely advise you to read about python's build-in input function because you've a misconception about what it does and doesn't. — Pedro Lobito
– Pedro Lobito, Commented Jun 14, 2020 at 11:44

Mathias R. Jessen · Accepted Answer · 2020-06-13 13:25:08Z

Why can't Powershell display a string when i use stdout in Python?

Because the stdout device interface may buffer writes to it, so either run python in unbuffered mode:

PS C:\> python -u script.py

or explicitly flush the buffer before reading stdin:

def get_int():
    sys.stdout.write("Enter number(s). ")
    sys.stdout.flush()
    return map(int, sys.stdin.readline().strip().split())

or you can replace sys.stdout with a wrapper that does it for you:

class Unbuffered(object):
   def __init__(self, stream):
       self.stream = stream
   def write(self, data):
       self.stream.write(data)
       self.stream.flush()
   def writelines(self, datas):
       self.stream.writelines(datas)
       self.stream.flush()
   def __getattr__(self, attr):
       return getattr(self.stream, attr)

sys.stdout = Unbuffered(sys.stdout)

# this will now flush automatically before calling stdin.readline()
sys.stdout.write("Enter something: ")
numbers = map(int, sys.stdin.readline().strip().split())

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