Selective Removal of Non-ASCII Characters

Working with textual data often involves the need to remove non-ASCII characters, while preserving certain symbols like spaces and periods. While basic filtering methods may remove all non-ASCII characters, this might not be desirable in some cases.

Let's consider the following code:

def onlyascii(char):
    if ord(char)  127: return ''
    else: return char

This code removes all characters with ASCII values less than 48 or greater than 127, effectively stripping the text of non-ASCII characters. However, it also removes spaces (ASCII 32) and periods (ASCII 46).

To selectively remove non-ASCII characters while preserving spaces and periods, we can leverage Python's string.printable module:

import string
printable = set(string.printable)
filtered_data = filter(lambda x: x in printable, data)

The string.printable set contains all printable characters on the system, including digits, letters, symbols, spaces, and periods. Using this set as a filter, we can remove all non-printable characters from the string.

For example, if we have the string "some\x00string. with\x15 funny characters":

s = "some\x00string. with\x15 funny characters"
''.join(filter(lambda x: x in printable, s))

The result will be:

'somestring. with funny characters'

This method effectively removes non-ASCII characters while preserving spaces and periods, providing a clean string for further processing.