Renaming the beginning of a file name in Python

I am attempting to create an executable that renames all files in its folder.

I am lost on how to reference (and add to) the beginning of a file name.

For example:

file_text.xlsx

What I need it to look like:

10-30-2021_file_text.xlsx

I would like to append to the beginning of the file name, and add my own string(s)

NOTE: 'file_text' are randomly generated file names, and all unique. So I would need to keep the unique names and just add to the beginning of each unique file name.

Here is what I have so far to rename the other files, I figured I could reference a space but this did not work as there are no spaces.

import os

directory = os.getcwd()

txt_replaced = ' '
txt_needed = '2021-10-31'

for f in os.listdir(directory):
    os.rename(os.path.join(directory, f),
                os.path.join(directory, f.replace(txt_needed, txt_replaced)))

I also am curious if there is a way to reference specific positions within the file name.

For example:

text_text1.csv

If there is a way to uppercase only 'text1'?

Thank you!

Solution

replace() doesn't work because there's no space character at the beginning of the filename. So there's nothing to replace.

You also didn't add the _ character after the date.

Just use ordinary string concatenation or formatting

for f in os.listdir(directory):
    os.rename(os.path.join(directory, f),
                os.path.join(directory, f"{txt_needed}_{f}"))