Python input() and print() not visible from a PowerShell class method: practical ways to restore interactive console I/O

Troubleshoot Python input() and print() not showing when run from a PowerShell class method. Learn fixes: use Read-Host args, forward output, and argparse tips

When a Python script that relies on input() and print() is launched directly from PowerShell, the prompt and the echoed response show up as expected. But the moment the same script is invoked inside a PowerShell class method, the interactivity appears to vanish: the Python process still runs, accepts input, and exits, yet nothing visible is printed to the console. Below is a minimal reproduction and several practical ways to regain interactive behavior without changing the underlying program logic.

Reproducing the issue

Consider a simple Python script:

# app.py
user_val = input("type your input: ")
print(f"your input is: {user_val}")

Now wrap the call to Python inside a PowerShell class and run it via a separate entry point:

# lib.psm1
class DataPipe{
    [string] $pyFile
    DataPipe([string] $pyPath){
        $this.pyFile = $pyPath        
    }
    [void] Invoke(){
        python $this.pyFile       
    }
}   

# start.ps1
using module .\lib.psm1
$job = [DataPipe]::new(".\app.py")
$job.Invoke()

In the terminal, you can type a value, but you won’t see the prompt or the final message:

PS C:\demo> .\start.ps1
test
PS C:\demo>

Attempts to surface the output via piping or flushing don’t help in this context:

# Inside lib.psm1 (did not help in this scenario)
python $this.pyFile | Write-Output
python $this.pyFile | Write-Host
python -v $this.pyFile | Write-Host
# Inside app.py (did not help in this scenario)
print(f"your input is: {user_val}", flush=True)
import sys; sys.stdout.write(f"your input is: {user_val}")

What’s going on

When the Python process is started from within the PowerShell class method, its standard output ends up being captured rather than written straight to the console. The effect is that the prompt emitted by print() isn’t displayed to the host; meanwhile, input() still waits for data, so your keystrokes are consumed even though you don’t see the interactive cue. Because the output is not forwarded to the host automatically in this shape, it looks like “nothing happens” even though the script is running.

Two reliable ways to restore interactivity

The simplest path is to move the interactive prompt to PowerShell, then pass the collected data to Python as arguments. This makes the user experience clear and the data flow explicit. Alternatively, if you need the Python script to print its own prompt, you can forward specific lines from the child process directly to the PowerShell host.

Approach 1: prompt in PowerShell and pass the value to Python as an argument.

# lib.psm1
class DataPipe {
    [string] $pyFile
    DataPipe([string] $pyPath) {
        $this.pyFile = $pyPath
    }
    [string[]] Invoke() {
        $val = Read-Host 'type your input'
        return python $this.pyFile $val
    }
}

# app.py
import sys
print(f"your input is: {sys.argv[1]}")

This keeps the interaction visible in the console and returns the Python process output to the caller in a predictable way by changing the method’s return type to string[].

Approach 2: let Python print the prompt, then explicitly write that prompt to the host in PowerShell.

# app.py
print("type your input:")
u = input()
print(f"your input is: {u}")

# lib.psm1
class DataPipe {
    [string] $pyFile
    DataPipe([string] $pyPath) {
        $this.pyFile = $pyPath
    }
    [string[]] Invoke() {
        $showFirst = $true
        $collected = python $this.pyFile | ForEach-Object {
            if ($showFirst) {
                Write-Host $_
                $showFirst = $false
                return
            }
            $_
        }
        return $collected
    }
}

Here the first line from Python is sent directly to the console via Write-Host, so the user sees the prompt at the right time. The remainder of the output is preserved as the method’s return value.

Feeding many inputs without clutter: argparse

If the Python side expects numerous inputs, gathering them in PowerShell and passing them as named parameters keeps the interface readable. On the Python side, use argparse to manage the parameters cleanly.

# app.py
import argparse
p = argparse.ArgumentParser()
p.add_argument("-paramfoo", type=str)
p.add_argument("-parambar", type=str)
for k, v in vars(p.parse_args()).items():
    print(f"input for parameter {k}: {v}")

# lib.psm1
class DataPipe {
    [string] $pyFile
    DataPipe([string] $pyPath) {
        $this.pyFile = $pyPath
    }
    [string[]] Invoke() {
        $foo = Read-Host 'type your input for -paramfoo'
        $bar = Read-Host 'type your input for -parambar'
        return python $this.pyFile -paramfoo $foo -parambar $bar
    }
}

This pattern keeps the console experience consistent while avoiding manual parsing on the Python side.

Why this matters

Bridging interactive behavior across processes can be subtle. When child process output is captured rather than written straight to the console, prompts disappear and user experience degrades. Making the interaction explicit—either by prompting in PowerShell and passing arguments to Python, or by selectively forwarding output lines to the host—restores clarity and control without changing the program’s intent.

Conclusion

If a Python script launched inside a PowerShell class method seems non-interactive, the output is likely being captured instead of displayed. Use Read-Host to collect user input in PowerShell and pass it as arguments, or forward the desired lines from the child process to the host with Write-Host. For scripts with many inputs, rely on argparse on the Python side and named arguments on the PowerShell side. These approaches keep interactivity visible, maintain predictable data flow, and avoid ad-hoc fixes that don’t surface output reliably.