Indexing is the way to identify a particular item in a sequence. R[3] identifies the fourth item of sequence R (remember, indexing starts at 0). What about identifying a block of items in a sequence? R[2:5] is the sequence starting with the third and going up to the sixth item of R. Slicing notation (with one colon) applied to a list or tuple always identifies a sequence (list or tuple), even if the length is 0 or 1. Slicing does not refer to an individual item the way that indexing does. For strings, slicing works differently: a slice of a string is always a string, but so is an indexed value in a string. Examples follow, including mixed examples that show indexing and slicing, and taking slices of slices.

Slicing Examples

Text = "certificate of product ratings"
a = Text[3:14]
b = Text[:12]
c = Text[:-18]
d = Text[Text.index("f"):len(Text)]
e = Text[10:10+5]
f = Text[13:13]
Items = [4,1,2,3,1,9,7,0,6]
g = Items[2:-2]
h = Items[2:9]
i = h[2:4]
j = Items[2:9][2:4]
k = h[1]
l = Items[2:9][1]