find 'yesterdays files'

[Gribouillis]

You could use pathlib and datetime modules

>>> from pathlib import Path
>>> import datetime as dt
>>>
>>> yesterday = dt.datetime.now().date() - dt.timedelta(days=1)
>>> f = Path('foo.png')
>>> if yesterday == dt.datetime.fromtimestamp(f.stat().st_mtime).date():
...     print('f was last modified yesterday')
... 
>>> 

Note that st_mtime gives modification time on all platforms, and st_ctime gives creation time in Windows but not necessarily in Linux.