Python: delete a item from a list

• remove the first matching element:

  if e in list:
      list.remove(e)

• remove all occurrences:

  while e in list:
      list.remove(e)

• EAFP style: remove the first occurrence:

  try:
      list.remove(e)
  except ValueError:
      # not in the list
      pass
  

• EAFP style: remove all occurrences:

  while True:
      try:
          list.remove(e)
      except ValueError:
          break
  

EAFP

Easier to ask for forgiveness than permission. This common Python coding style assumes the existence of valid keys or attributes and catches exceptions if the assumption proves false. This clean and fast style is characterized by the presence of many try and except statements. The technique contrasts with the LBYL style common to many other languages such as C.

python: join lists

list1 = ['a', 'b']
list2 = ['c', 'd']

list3 = list1 + list2

Python: check if a list is empty

    if not a:
        print('empty')

Python: list comprehension

• To transform a list to another:

  list2 = [ unicode(e.strip()) for e in list1 ]
  

• To transform a list to another conditionally:

  list2 = [ unicode(e.strip()) if e is not None else '' for e in list1 ]