Pythonic way to subtract one list from another with validation of presence
A good pythonic way to subtract one list from another is to use list comprehension: # remove all elements of list2 from list1 list1 = [x for x in list1 if x not in list2] How would I, in the same step, validate that each x actually occurs in list1 (e.g. in order to raise an error on missing elements)?
You don't need to check. x by definition has to be in list1, or else the iterator wouldn't provide it (since you're iterating over list1's items) But in case it might get modified while you're iterating (which is a case you should definitely avoid): list1 = [x for x in list1 if x not in list2 and x in list1] If you need more complex behaviour like showing an error message, use an explicit loop list_delta =  for x in list1: if x not in list1: raise IndexError("oh god what") if x not in list2: list_delta.append(x) But honestly this seems like an X-Y problem because you should never have to do this to begin with.
I'm not sure I understand what you're asking there, but if the order doesn't matter and there are no repetitions, you can use set difference as #Chih-Hsu Jack Lin mentioned in the comments: list(set(list1) - set(list2)) And if order doesn't matter, but element count does matter, another approach is to use collections.Counter: list((Counter(list1) - Counter(list2)).elements())
How to animate font size without text reordering, when `text_size=self.size`
How to import the last row from array of excel files to another excel using openpyxl
how to terminate a thread which calls the webbrowser in python
Can I load HTML on Ghost.py
Combining two lists of names and sorting them to make one sorted list of names
Python equivalent of bash sort lexicographical and numerical
Why isn't my frames background showing?
Trying to do a natural join using python standard library
How to combine several querysets by key in common?
How I can speed up row column access to pandas dataframe?
Create list with combinations of 3 elements of other list with repetitions
PyQt5 does not change gifs
Pydub - combine split_on_silence with minimum length / file size
how to choose python version accordingly in pycharm?
Unable to import Flask to Kivy iOS
Unique list without spliting entries based on spaces in python