The type() Function and Lists in Python

The type() function in Python is used to determine the type of an object. When used with lists, it provides insights into the nature of lists themselves and the elements they contain.

• Type of a ListWhen you use type() on a list, it returns the type of the list object.

Example: 

my_list = [1, 2, 3, 4]
print(type(my_list))  # Output: <class 'list'>

This result indicates that my_list is an instance of the list class.

•  Type of Elements in a List

You can use type() to check the type of individual elements within a list. This is useful for data validation or conditional operations based on element types.

Example: 

my_list = [1, 'text', 3.14, [5, 6], True]
for element in my_list:
    print(type(element))
"""
Output:
<class 'int'>
<class 'str'>
<class 'float'>
<class 'list'>
<class 'bool'>
"""

 This shows that my_list contains elements of various types: int, str, float, list, and bool.

• Type Checking of Nested Lists

When you have nested lists, you can use type() to check the types of sub-lists and elements within these sub-lists.

Example: 

nested_list = [
    [1, 2, 3],      # Sub-list 1
    ['a', 'b'],     # Sub-list 2
    [True, False]   # Sub-list 3
]
# Check the type of each sub-list
for sublist in nested_list:
    print(type(sublist))
"""
Output:
<class 'list'>
<class 'list'>
<class 'list'>
"""

 This indicates that each element in nested_list is also a list.

• Type Checking of Elements in Nested Lists

To check the types of elements inside sub-lists, you can use type() on those elements.

Example: 

nested_list = [
    [1, 2, 3],
    ['a', 'b'],
    [True, False]
]
# Check the types of elements in each sub-list
for sublist in nested_list:
    for element in sublist:
        print(type(element))
"""
Output:
<class 'int'>
<class 'int'>
<class 'int'>
<class 'str'>
<class 'str'>
<class 'bool'>
<class 'bool'>
"""

 This result shows the types of elements within each sub-list.

• Using type() to Check for Lists

You can use type() to verify if an object is a list or not, and also to check the types of list elements.

Example: 

def check_if_list(obj):
    if type(obj) is list:
        print("It's a list")
    else:
        print("It's not a list")
# Test different variables
check_if_list([1, 2, 3])  # Output: It's a list
check_if_list("text")    # Output: It's not a list
check_if_list(123)        # Output: It's not a list

•  Comparison with Other Functions

isinstance() vs type()

• type() returns the exact type of an object.
• isinstance() checks if an object is an instance of a class or a subclass, which is often more flexible.

Example: 

my_list = [1, 2, 3]
print(type(my_list) == list)  # Output: True
print(isinstance(my_list, list))  # Output: True
print(isinstance(my_list, object))  # Output: True (since all classes inherit from `object`)

 Key Points Summary

• Determining Type: Use type() to get the type of a list and its elements.
• Nested Lists: Use type() to check the types of sub-lists and elements within sub-lists.
• Comparison with isinstance(): type() gives the exact type, while isinstance() is more flexible for type checks in class hierarchies.