Python: single colon vs double colon

Question

What is the difference between single and double colon in this situation? data[0:,4] vs data[0::,4]

women_only_stats = data[0::,4]         


        

Answer 1

Both syntaxes result in the same indexes.

class Foo(object):
  def __getitem__(self, idx):
    print(idx)

Foo()[1::,6]
# prints (slice(1, None, None), 6)
Foo()[1:,6]
# prints (slice(1, None, None), 6)

Basically, 1::,6 is a tuple of a slice (1::) and a number (6). The slice is of the form start:stop[:stride]. Leaving the stride blank (1::) or not stating it (1:) is equivalent.