Working with Lists¶
In earlier chapters we worked with lists of numbers as shown below.
But a list in Python can also hold different types of things in the same list, like numbers and strings. You start and end a list with square brackets ([]) and separate elements with commas as shown in line 1 below.
The function len will return the number of items in the list. You can do “arithmetic” with lists using * and +, just like you can with strings. Multiplication repeats items in the list. We can add two lists together, even if one of the lists only has a single item in it.
Activity: CodeLens 2 (Simple_Lists)
- 1
- This is just how many numbers are in the list. There are also strings in this list.
- 3
- This is just the number of strings in this list. There is also a number in this list.
- 4
- This is the number of items in this list. There are 3 strings and 1 number.
- 14
- Count each string as one item.
csp-16-3-3: What is the length of the list [“Sue”,”Maria”,5,”Erica”]?
- 1
- That is the number of items in the list start on line 1, but line 2 adds more.
- 2
- That is how many items were in the list that was added to start. But, start already had one element.
- 3
- The list start has one item and then two more were added.
csp-16-3-4: What would the following code print?
start = [3]
start = start + [6,7]
print (len(start))
Note
Remember that a list starts with a [ and ends with a ]. Items in the list are separated by commas.
Run the code below to see what type of error you get if you forget the ending ] as shown below on line 1. Also see what happens if you don’t separate the list items with commas as shown on line 2. Fix the code to run and print.