I use this note for only tricks in Python (quick exercises solution also).

Check string

• Check ASCII

    is_ascii = lambda s: len(s) == len(s.encode())
  

• Check there is any digit numbers?

    has_digit = lambda s: any(char.isdigit() for char in s)
  

• s.isupper(), s.islower()

List

• Delete all same element ‘a’ from list

  arr = [x for x in arr if x != 'a']
  

  Note that, if we only want to delete 1 element a, use arr.remove('a')

• Remove duplicates and only keep 1 of them: change to set: b = set(a) where a is a list