Is there a simple way to delete a list element by value?

Question

I want to remove a value from a list if it exists in the list (which it may not).

a = [1, 2, 3, 4]
b = a.index(6)

del a[b]
print(a)

The abov

Answer 1

Finding a value in a list and then deleting that index (if it exists) is easier done by just using list's remove method:

>>> a = [1, 2, 3, 4]
>>> try:
...   a.remove(6)
... except ValueError:
...   pass
... 
>>> print a
[1, 2, 3, 4]
>>> try:
...   a.remove(3)
... except ValueError:
...   pass
... 
>>> print a
[1, 2, 4]

If you do this often, you can wrap it up in a function:

def remove_if_exists(L, value):
  try:
    L.remove(value)
  except ValueError:
    pass