Overriding Standard Output

Argenta provides flexible mechanisms for output formatting, including dynamic dividing lines. This is achieved by intercepting the standard output stream (stdout), which imposes certain specifics.

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When to Disable stdout Interception

Disable stdout interception (disable_redirect_stdout=True in Router) if your commands:

✓ Use input() for interactive user input

✓ Use progress bars (tqdm, rich.progress)

✓ Output data in real-time (streaming, logs)

✓ Use libraries that work directly with stdout

For regular commands with print(), interception can be left enabled — it does not affect their operation.

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stdout Interception Mechanism

By default, Argenta intercepts all text output to stdout inside a command handler. This is necessary to implement dynamic dividers: the system analyzes the output, finds the longest line, and uses it to draw the top and bottom borders. This approach creates a neat interface where the command output is “wrapped” in a frame fitted to its content.

Example of an application with a dynamic dividing line:

As you can see, the dividing line is exactly the same length as the longest line in the output.

The same application with a static line:

In this example, the dividing line has a fixed length (25 characters by default).

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Side Effects of stdout Interception

A side effect of this mechanism manifests when using functions that sequentially output text to the console and expect user input. A classic example is the standard input() function.

user_name = input("Enter your name: ")
print(f"Привет, {user_name}!")

Warning

With stdout interception enabled, text (for example, "Enter your name: ") will not be output to the console immediately. It will go into a buffer and appear only after the handler finishes, along with the rest of the output. This can confuse the user.

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Disabling stdout Interception with disable_redirect_stdout

To solve this problem, the Router constructor provides a special argument:

• disable_redirect_stdout (bool, default False)

If you set disable_redirect_stdout=True when creating a router, the stdout interception mechanism will be disabled for all its handlers.

Usage example:

from argenta import Response, Router

# For this router stdout redirect will be disabled
interactive_router = Router(disable_redirect_stdout=True)


@interactive_router.command("ask")
def ask_name(response: Response):
    name = input("What is your name? ")
    print(f"Nice to meet you, {name}!")

In this case, input() will work as usual, and the user will immediately see the input prompt.

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Types of Dividing Lines

Argenta supports two types of dividers, which are configured during App initialization:

1. ``DynamicDividingLine()``

   • Default behavior. The line length dynamically adjusts to the longest text in the output.

   • Requires enabled stdout interception (disable_redirect_stdout=False in the router).

2. ``StaticDividingLine(length: int = 25)``

   • The line has a fixed length (25 characters by default), which can be set via the length argument.

   • Used forcibly for routers with disable_redirect_stdout=True, as it is impossible to determine dynamic length without output interception.

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Configuring the Dividing Line in App

You can globally set the divider type for the entire application via the dividing_line argument in the App constructor.

Usage example:

from argenta import App
from argenta.app import StaticDividingLine

# All routers will use static line with length 50 by default
app = App(dividing_line=StaticDividingLine(length=50))

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Resulting Behavior

disable_redirect_stdout on Router	Line type in App	Actual behavior	Does input() work correctly?
False (default)	DynamicDividingLine	Dynamic line, length by content	No
False (default)	StaticDividingLine	Static line of specified length	No
True	DynamicDividingLine	Forcibly static line (default length)	Yes
True	StaticDividingLine	Static line of specified length	Yes

Thus, for interactive commands that require user input, disable stdout interception at the router level. For all other commands, you can leave the default behavior.