Python: determine if all items of a list are the same item [duplicate]

Answer 1

def all_same(items):
    return all(x == items[0] for x in items)

Example:

>>> def all_same(items):
...     return all(x == items[0] for x in items)
...
>>> property_list = ["one", "one", "one"]
>>> all_same(property_list)
True
>>> property_list = ["one", "one", "two"]
>>> all_same(property_list)
False
>>> all_same([])
True

Answer 2

I originally interpreted you to be testing identity ("the same item"), but you're really testing equality ("same value"). (If you were testing identity, use is instead of ==.)

def all_same(items):
  it = iter(items)
  for first in it:
    break
  else:
    return True  # empty case, note all([]) == True
  return all(x == first for x in it)

The above works on any iterable, not just lists, otherwise you could use:

def all_same(L):
  return all(x == L[0] for x in L)

(But, IMHO, you might as well use the general version—it works perfectly fine on lists.)

Answer 3

You could cheat and use set:

def all_same( items ):
    return len( set( items ) ) == 1 #== len( items )

or you could use:

def all_same( items ):
    return all( map(lambda x: x == items[0], items ) )

or if you're dealing with an iterable instead of a list:

def all_same( iterable ):
    it_copy = tee( iterable, 1 )
    return len( set( it_copy) ) == 1

Answer 4

This is likely to be faster if you know values are in a list.

def all_same(values):
    return values.count(values[0]) == len(values)

Answer 5

Best way to do this is to use Python sets.You need to define all_same like this:

def all_same(items):
    return len(set(items)) < 2

Test:

>>> def all_same(items):
...     return len(set(items)) < 2
... 
>>> 
>>> property_list = ["one", "one", "one"]
>>> all_same(property_list)
True
>>> property_list = ["one", "one", "two"]
>>> all_same(property_list)
False
>>> property_list = []
>>> all_same(property_list)
True

Answer 6

This works both for sequences and iterables:

def all_same(items):
  it = iter(items)
  first = next(it, None)
  return all(x == first for x in it)