How to Provide Default Values for User Input with Editing Capabilities in Python?

Editing Input with Default Values in Python

When accepting user input with the input() function, it's often desirable to provide a default value that serves as a placeholder or starting point. In this case, a user wants to accept input for a folder name with the default value "Download" but allow the user to edit it easily by simply adding or removing characters.

The standard input() and raw_input() functions do not support this behavior out of the box. However, on Linux systems, the readline module offers a solution.

Using Readline

The readline module provides advanced line editing functionality. By defining a custom input function that utilizes readline, you can achieve the desired behavior. Here's an example:

<code class="python">import readline

def rlinput(prompt, prefill=''):
   readline.set_startup_hook(lambda: readline.insert_text(prefill))
   try:
      return input(prompt)  # or raw_input in Python 2
   finally:
      readline.set_startup_hook()</code>

In this function:

• rlinput(prompt, prefill) takes a prompt and an optional prefill value.
• readline.set_startup_hook sets a startup hook that inserts the prefill value into the prompt.
• input or raw_input is used to accept user input, allowing editing of the prefill.
• The finally block resets the startup hook to its default behavior.

Usage

To use this function, simply replace the standard input() call with the rlinput() function:

<code class="python">folder = rlinput('Folder name: ', 'Download')</code>

This will display the prompt "Folder name: Download" with the prefilled text "Download". If the user presses enter without making any changes, the default value will be saved as "Download". If the user wants to edit the default, they can simply type over or add characters to the prefilled text.

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