The problem with many other answers is that they only deal with character substitutions; not other issues.
Here is a comprehensive universal solution. It handles all types of issues for you, including (but not limited too) character substitution. It should cover all the bases.
Works in Windows, *nix, and almost every other file system.
def txt2filename(txt, chr_set='printable'):
"""Converts txt to a valid filename.
Args:
txt: The str to convert.
chr_set:
'printable': Any printable character except those disallowed on Windows/*nix.
'extended': 'printable' + extended ASCII character codes 128-255
'universal': For almost *any* file system. '-.0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
"""
ext = '' if '.' not in txt else txt[txt.rfind('.'):]
FILLER = '-'
MAX_LEN = 255 # Maximum length of filename is 255 bytes in Windows and some *nix flavors.
# Step 1: Remove excluded characters.
BLACK_LIST = set(chr(127) + r'<>:"/\|?*') # 127 is unprintable, the rest are illegal in Windows.
white_lists = {
'universal': {'-.0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'},
'printable': {chr(x) for x in range(32, 127)} - BLACK_LIST, # 0-32, 127 are unprintable,
'extended' : {chr(x) for x in range(32, 256)} - BLACK_LIST,
}
white_list = white_lists[chr_set]
result = ''.join(x
if x in white_list else FILLER
for x in txt)
# Step 2: Device names, '.', and '..' are invalid filenames in Windows.
DEVICE_NAMES = 'CON,PRN,AUX,NUL,COM1,COM2,COM3,COM4,' \
'COM5,COM6,COM7,COM8,COM9,LPT1,LPT2,' \
'LPT3,LPT4,LPT5,LPT6,LPT7,LPT8,LPT9,' \
'CONIN$,CONOUT$,..,.'.split() # This list is an O(n) operation.
if result in DEVICE_NAMES:
result = f'-{result}-'
# Step 3: Truncate long files while preserving the file extension.
result = result[:MAX_LEN - len(ext)] + ext
# Step 4: Windows does not allow filenames to end with '.' or ' ' or begin with ' '.
result = re.sub(r'^[. ]', FILLER, result)
result = re.sub(r' $', FILLER, result)
return result
It replaces non-printable characters even if they are technically valid filenames because they are not always simple to deal with.
No external libraries needed.
