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

.sort( )

The sort method is used for the same purpose that our previous sorted function is used for; however, it will change the original list directly:

# sorting a list with .sort() in-place nums = [5, 0, 8, 3] nums.sort( ) # alters the original variable directly print(nums)

Go ahead and run that cell. The resulted output will be a properly sorted list. Just remember that the nums variable is now changed, as .sort() changes the value directly.

Conditionals and Lists

When working with lists, often you’ll need to check if values exist. Now we’ll introduce how to run conditional statements on a list. There are many reasons to run a conditional on a list; these are simply a couple examples.

Using “in” and “not in” Keywords

We’ve seen the use of these keywords already, when we covered conditional statements last week. When working with lists, they serve a purpose to find values within the list quickly:

# using conditional statements on a list names = [ "Jack", "Robert", "Mary" ] if "Mary" in names:
print("found") # will run since Mary is in the list if "Jimmy" not in names: print("not found") # will run since Jimmy is not in the list

Go ahead and run that cell. The output results in “found” and “not found”. On the first statement, we were trying to see if “Mary” existed in the list, which it does. The second conditional statement checked to see if “Jimmy” did not exist, which is also true, so it too runs.

Checking an Empty List

There are so many reasons to need to check for an empty list. It’s usually to ensure you don’t cause any errors in your program, so let’s see how we can check:

# using conditionals to see if a list is empty nums = [ ] if not nums: # could also say 'if nums == []' print("empty")

Go ahead and run that cell. This will output “empty”. It’s mentioned in the comment, but we could have also checked to see if it were equal to empty brackets. Here, I wanted to show you how to use the “not” keyword. To check for a list with items, you would write the following:
>>> if nums: