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

In your case data is

data = ['1' '0' '3' 'Braund, Mr. Owen Harris' 'male' '22' '1' '0' 'A/5 21171' '7.25' '' 'S']

So it is equal to

data = ['103Br.............7.25S']

In this sitation there is only single item in list so data[0::4] or data[0:4] doesn't impact any thing.

If you try this it will clear your question/answer

print data[0][0::4]
print data[0][0:4] 

It works like

data[start:end:step]

So it behaves as usual if your step size is less then data length.