如何覆寫動態 FTP 下載程式進度顯示先前的列印輸出？

Overwriting Previous Print Output: Enhancing FTP Downloader Progress Display

In the process of creating an FTP downloader, it's desirable to have a progress display that continuously updates, overwriting previous output on the same line. Imagine a scenario where you're downloading a file and want to monitor its progress in real-time without the cluttering of multiple print lines.

The initial code used to handle the progress display relied on the following structure:

print(os.path.getsize(file_name) / 1024, 'KB / ', size, 'KB downloaded!')

This would output a new line each time the progress updated. To achieve the desired effect of overwriting the previous line, the end keyword can be utilized. Here's the revised code:

print(os.path.getsize(file_name) / 1024, 'KB / ', size, 'KB downloaded!', end='\r')

The crucial difference here is the addition of end='\r' at the end of the print statement. By default, the print() function adds a newline character (\n) at the end of its output. However, using end='\r' replaces this newline with a carriage return (\r) instead.

When a carriage return is used, the cursor returns to the beginning of the current line without creating a new one. This allows the subsequent progress updates to overwrite the previous line, effectively creating a dynamic progress display.

Note that this approach is compatible with Python 3.x. For Python 2.6+, you may need to include the line from __future__ import print_function at the top of the file to use the enhanced print() function with keyword arguments.

By incorporating this simple modification, you can create a streamlined progress display that keeps users informed without overwhelming them with multiple lines of output.

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