Python String Slicing - Learn By Example

To access a range of characters in a string, you need to slice a string. One way to do this is to use the simple slicing operator :

With this operator you can specify where to start the slicing, where to end and specify the step.

Slicing a String

If S is a string, the expression S [ start : stop : step ] returns the portion of the string from index start to index stop, at a step size step.

Here is a basic example of string slicing.

S = 'ABCDEFGHI'
print(S[2:7])	# CDEFG

Note that the item at index 7 'H' is not included.

You can also specify negative indices while slicing a string.

S = 'ABCDEFGHI'
print(S[-7:-2])	# CDEFG

You can specify both positive and negative indices at the same time.

S = 'ABCDEFGHI'
print(S[2:-5])	# CD

You can specify the step of the slicing using step parameter. The step parameter is optional and by default 1.

# Return every 2nd item between position 2 to 7
S = 'ABCDEFGHI'
print(S[2:7:2])	# CEG

You can even specify a negative step size.

# Returns every 2nd item between position 6 to 1 in reverse order
S = 'ABCDEFGHI'
print(S[6:1:-2])    # GEC

Omitting the start index starts the slice from the index 0. Meaning, S[:stop] is equivalent to S[0:stop]

# Slice first three characters from the string
S = 'ABCDEFGHI'
print(S[:3])    # ABC

Whereas, omitting the stop index extends the slice to the end of the string. Meaning, S[start:] is equivalent to S[start:len(S)]

# Slice last three characters from the string
S = 'ABCDEFGHI'
print(S[6:])    # GHI

You can reverse a string by omitting both start and stop indices and specifying a step as -1.

S = 'ABCDEFGHI'
print(S[::-1])    # IHGFEDCBA