Python slice()

The slice() function returns a slice object that can use used to slice strings, lists, tuple etc.

The slice object is used to slice a given sequence (string, bytes, tuple, list or range) or any object which supports sequence protocol (implements __getitem__() and __len__() method).

The syntax of slice() is:

slice(start, stop, step)

slice() Parameters

slice() can take three parameters:

  • start (optional) - Starting integer where the slicing of the object starts. Default to None if not provided.
  • stop - Integer until which the slicing takes place. The slicing stops at index stop -1 (last element).
  • step (optional) - Integer value which determines the increment between each index for slicing. Defaults to None if not provided.

Example 1: Create a slice object for slicing

# contains indices (0, 1, 2)
result1 = slice(3)
print(result1)

# contains indices (1, 3)
result2 = slice(1, 5, 2)
print(slice(1, 5, 2))

Output

slice(None, 3, None)
slice(1, 5, 2)

Here, result1 and result2 are slice objects.

Now we know about slice objects, let's see how we can get substring, sub-list, sub-tuple, etc. from slice objects.


Example 2: Get substring using slice object

# Program to get a substring from the given string 

py_string = 'Python'

# stop = 3
# contains 0, 1 and 2 indices
slice_object = slice(3) 
print(py_string[slice_object])  # Pyt

# start = 1, stop = 6, step = 2
# contains 1, 3 and 5 indices
slice_object = slice(1, 6, 2)
print(py_string[slice_object])   # yhn

Output

Pyt
yhn

Example 3: Get substring using negative index

py_string = 'Python'

# start = -1, stop = -4, step = -1
# contains indices -1, -2 and -3
slice_object = slice(-1, -4, -1)

print(py_string[slice_object])   # noh

Output

noh

Example 4: Get sublist and sub-tuple

py_list = ['P', 'y', 't', 'h', 'o', 'n']
py_tuple = ('P', 'y', 't', 'h', 'o', 'n')

# contains indices 0, 1 and 2
slice_object = slice(3)
print(py_list[slice_object]) # ['P', 'y', 't']

# contains indices 1 and 3
slice_object = slice(1, 5, 2)
print(py_tuple[slice_object]) # ('y', 'h')    

Output

['P', 'y', 't']
('y', 'h')

Example 5: Get sublist and sub-tuple using negative index

py_list = ['P', 'y', 't', 'h', 'o', 'n']
py_tuple = ('P', 'y', 't', 'h', 'o', 'n')

# contains indices -1, -2 and -3
slice_object = slice(-1, -4, -1) 
print(py_list[slice_object])  # ['n', 'o', 'h']

# contains indices -1 and -3
slice_object = slice(-1, -5, -2)
print(py_tuple[slice_object]) # ('n', 'h')

Output

['n', 'o', 'h']
('n', 'h')

Example 6: Using Indexing Syntax for Slicing

The slice object can be substituted with the indexing syntax in Python.

You can alternately use the following syntax for slicing:

obj[start:stop:step]

For example,

py_string = 'Python'

# contains indices 0, 1 and 2
print(py_string[0:3])  # Pyt

# contains indices 1 and 3
print(py_string[1:5:2]) # yh

Output

Pyt
yh