Part 4, More Loops
And we’re back (after a slight hiatus)! Let another day of Python begin!! So let’s back up for a second. We can make variables really easily:
x=5 y=6 z=7 a=8 b=9#and so forth
And right now if we wanted to print out all the numbers between 1 and 100 we could do this:
num=0 while num <= 100: print(num) num = num +1
This will print all the numbers between 0 and 100 (inclusive). Okay now for the new stuff. Let’s say we were in a classroom, in that class we have a bunch of students.
student1 = "Jacob" student2 = "Sam" student3 = "Corey" student4 = "Michael" #If we wanted to print each student: print(student1) print(student2) print(student3) print(student4)
As you can tell this is a bit annoying, lets say (theoretically) our classroom had 100 kids, we would have to write 100 print statements! In order to make this easier we can have a list of students.
students = ["Jacob", "Sam", "Corey", "Michael"]
So now we have a list of four students. Right now the only way we can print out each student is like this:
num = 0 while num<len(students): #len is a built in function like print that tells us how long something is, it could be an array, a string, etc. print(students[num]) num = num + 1
We access what’s called an index in our array with [somenumber]. But be careful with this, because if the length of our array is 4 and we ask for the object at the fifth index: students (keep in mind that programmers start counting at 0) we’ll get an error! The easiest way to avoid this is by using a new kind of loop!
for student in students: print(student)
The magical for loop can do some awesome stuff. We can use it to iterate through a list, a string, and even a range of numbers!
for num in range(0,10):#range is another built in function in python print(num)#prints 0 through 9
With python, we can have lists of strings, and numbers together. Lists have some built in functions that are really useful:
list = ["string1",10,"string2",100] if 10 in list: list.remove(list.index(10)) list.insert(3,300) for thing in list: print(thing)
Here are some of the functions of array:
- list.append(obj) #add an object to the end of an array
- list.count(obj) #count the amount of times the object shows up in the array
- list.index(obj) #where’s the first occurance of the object
- list.insert(index, obj) #put an object at a certain place
- list.remove(obj) #get rid of an object if it’s there
Next time we’re going to go over a different kind of list called a dictionary. In the meantime, I’d suggest to make a program that uses lists and some of the other things we’ve learned.