List tools

Handy list tools:

nums = [5, 2, 9]
nums.sort()        # sorts in place -> [2, 5, 9]
nums.insert(0, 1)  # put 1 at index 0
nums.remove(5)     # remove the first 5
last = nums.pop()  # remove & return the last item
9 in nums          # membership test -> bool
sum(nums)         # total of the numbers
min(nums), max(nums)  # smallest and largest
ordered = sorted(nums)  # new sorted list; nums is unchanged
nums.count(2)     # number of occurrences of 2
ordered[:2]      # first two items; list slices work like string slices

A for loop goes straight through the items: for n in nums:

See it run

nums = [4, 1, 3]
ordered = nums.sort()
print(ordered)
print(nums)

sort() changes the list itself. Watch what it hands back.

Practice list tools

Exercise 1

With scores = [72, 95, 88, 61]:

sort scores in place (ascending)
best = the highest score
average = the mean, using sum and len (79.0)

Exercise 2

Use the week's temps in the editor below.

The 30 was a glitch: remove it by value.
A late reading of 22 belongs at the start: insert it at index 0.
Then set hottest, coldest and spread (hottest minus coldest).

Exercise 3

Use the race times in the editor below, measured in seconds (lower is faster). Without changing times:

podium = a new list of the three fastest times, fastest first
ties = how many runners share the fastest time (use .count)
in_time = True if 60.3 is in the list (use in)

The explanation and tasks are public. Running this lesson requires an account with course access.

Practice

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Visualizer Watch your code run line by line

Run your code, then choose Play to follow its execution.

Memory · names → values

Variables appear here as Python creates them.

Output & plots