Python Projects for Beginners a ten-Week Bootcamp Approach to Python Programming

Declaring a List of Mixed Data Types

Lists can hold any data type, even other lists. Let’s check out an example of several data types:

# declaring a list of mixed data types num = 4.3 data = [num, "word", True] # the power of data collection print(data)

Go ahead and run that cell. This will output [4.3, ‘word’, True]. It outputs 4.3 as the first item because when the list is defined, it stores the value of num, not the variable
itself.

Lists Within Lists

Let’s get a little more complex and see how lists can be stored within another list:

# understanding lists within lists
data = [5, "book", [ 34, "hello" ], True] # lists can hold any type print(data) print( data[2] )

Go ahead and run that cell. This will output [5, ‘book’, [34, ‘hello’], True] and [34, ‘hello’]. The first output is the entire data variable’s value, which stores an integer, a string, a list, and a boolean data type. The second output is the list stored inside of our data variable, which is located at index 2 and includes an integer and string data type.

Accessing Lists Within Lists

In the last cell, we saw how to output the list stored within the data variable. Now, we’ll see how we can access the items within the inner list. To access items within a list normally, we simply use bracket notation and the index location. When that item is another list, you simply add a second set of brackets after the first set. Let’s check out an example and come back to it:

# using double bracket notation to access lists within lists print( data[2][0] ) # will output 34 inner_list = data[2] # inner list will equal [34, 'hello'] print( inner_list[1] ) # will output 'hello'

Go ahead and run that cell. The first output will be 34. This is because our first index location is accessing the second index in data, which is a list. Then the second index location specified is accessing the value in that list at location zero, which results in the integer of 34. The second output is “hello”. We get this result because we declared a
ChApter 4 LIsts And Loops
variable to store the value at index 2 of our data variable, which happens to be a list. Our inner_list variable is now equal to [34, ‘hello’] and we access the value at index 1, which is the string “hello”. To get a little bit more understanding of how multi-indexing works, check out Table 4-1.
Table 4-1. Multi-indexing values