String Slicing

String slicing allows you to extract a portion of a string.

It takes two parameters: the starting index and the ending index (optional). It returns a new string containing the extracted portion.

Let's perform such operations on the string "computer". Its structure is the following:

Single argument slicing

Positive argument slicing

str = "computer" print(str[3:])

Output:

puter

In this example, str[3:] skips the first 3 symbols of the string - c, o, and m.

The rest of the string (starting from the 3rd index - p) is extracted - puter.

Negative argument slicing

Negative indexes track the string characters in reverse.

str = "computer" print(str[-3:])

Output:

ter

In this example, str[-3:] extracts only the last 3 symbols of the string - t, e, and r.

Two arguments slicing

Positive arguments slicing

str = "computer" print(str[3:5])

Output:

pu

In this example, str[3:5] skips the first 3 symbols of the string - c, o, and m.

Then it takes the rest of the string until it reaches the 5th symbol - u.

Negative arguments slicing

str = "computer" print(str[-5:-2])

Output:

put

In this example, str[-5:-2] starts slicing at the 5th symbol counting backwards and ends before the second symbol counting backwards.

Mixed arguments slicing

Both positive and negative arguments can be specified.

str = "computer" print(str[1:-1])

Output:

ompute

In this example, str[1:-1] starts after the first symbol and ends before the last symbol.

Invalid cases

An invalid case simply returns an empty string. In such cases, the slicing start argument position is after the slicing end.

Example of a valid and invalid case:

str = "computer" valid_case = str[1:-1] invalid_case = str[-1:1] print(valid_case) print(len(valid_case)) print(len(invalid_case))

Output:

ompute 6 0

Another invalid slicing case is specifying a starting argument that's beyond the string's bounds:

str = "computer" valid_case1 = str[3:] valid_case2 = str[0:100] invalid_case = str[9:] print(valid_case1) print(valid_case2) print(len(invalid_case))

Output:

puter computer 0

Three arguments slicing

The third argumen allows you to specify an additional step (also known as the stride) to skip characters in the range while slicing.

str = "abcabcabcabc" slice_result = str[::3] print(slice_result)

Output:

aaaa

In this example 3 specifies that every 3rd symbol of the string must be extracted.

It can be combined with the other arguments to slice only in a certain range and with specific step:

str = "-----smartphone*****" slice_result = str[5:-5:3] print(slice_result)

Output:

srhe

In this case the first argument (5) skips the first 5 symbols - -----.

The second argument (-5) skips the last 5 symbols - *****.

The third argument takes every 3rd symbol of the sliced string (smartphone) - s, r, h and e.