Extract part of string based on a template in Python

Question

I'd like to use Python to read in a list of directories and store data in variables based on a template such as /home/user/Music/%artist%/[%year%] %album% .

An example would be:

artist, year, album = None, None, None

template = "/home/user/Music/%artist%/[%year%] %album%"
path = "/home/user/Music/3 Doors Down/[2002] Away From The Sun"

if text == "%artist%":
    artist = key

if text == "%year%":
    year = key

if text == "%album%":
    album = key

print(artist)
# 3 Doors Down

print(year)
# 2002

print(album)
# Away From The Sun

I can do the reverse easily enough with str.replace("%artist%", artist) but how can extract the data?

Answer 1

If your folder structure template is reliable the following should work without the need for regular expressions.

path = "/home/user/Music/3 Doors Down/[2002] Away From The Sun"

path_parts = path.split("/") # divide up the path into array by slashes

print(path_parts)  

artist = path_parts[4] # get element of array at index 4

year = path_parts[5][1:5] # get characters at index 1-5 for the element of array at index 5

album = path_parts[5][7:]

print(artist)
# 3 Doors Down

print(year)
# 2002
    
print(album)
# Away From The Sun
    
# to put the path back together again using an F-string (No need for str.replace)
reconstructed_path = f"/home/user/Music/{artist}/[{year}] {album}"
    
print(reconstructed_path)

output:

['', 'home', 'user', 'Music', '3 Doors Down', '[2002] Away From The Sun']
3 Doors Down
2002
Away From The Sun
/home/user/Music/3 Doors Down/[2002] Away From The Sun

Answer 2

The following works for me:

from difflib import SequenceMatcher

def extract(template, text):
    seq = SequenceMatcher(None, template, text, True)
    return [text[c:d] for tag, a, b, c, d in seq.get_opcodes() if tag == 'replace']

template = "home/user/Music/%/[%] %"
path = "home/user/Music/3 Doors Down/[2002] Away From The Sun"

artist, year, album = extract(template, path)

print(artist)
print(year)
print(album)

Output:

3 Doors Down
2002
Away From The Sun

Each template placeholder can be any single character as long as the character is not present in the value to be returned.