Python helper functions that I don't want to rewrite

helpers.py

def replace_str_index(text, index=0, replacement=''):
    '''Replaces an index in a string with a replacement char/string'''
    return '{}{}{}'.format(text[:index], replacement, text[index+1:])

def get_substrings(string):
    '''Returns a list of all substrings in a string'''
    length = len(string)
    return [string[i:j+1] for i in range(length) for j in range(i, length)]

def copy_to_clipboard(string):
    '''Copies the string to the clipboard'''
    import sys
    import subprocess
    
    commands = {'win32': 'clip',
                'cygwin': 'clip',
                'darwin': 'pbcopy',
    }

    currentPlatform = sys.platform
    if currentPlatform not in commands:
        raise KeyError('Platform not supported')
    copyCommand = commands[currentPlatform]
    subprocess.Popen([copyCommand], stdin=subprocess.PIPE, encoding='utf8').communicate(string)