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Integers, Floats and Strings 3
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Variables IntroductionLecture1.1
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String FunctionalityLecture1.2
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More FunctionalityLecture1.3
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If Statements 3
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Boolean ValuesLecture2.1
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If StatementsLecture2.2
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Advanced If StatementsLecture2.3
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Lists, Sets and Tuples 5
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ListsLecture3.1
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IndexingLecture3.2
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More IndexingLecture3.3
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Advanced List FunctionsLecture3.4
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SetsLecture3.5
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Loops 3
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Looping over a RangeLecture4.1
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More List FunctionalityLecture4.2
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While LoopLecture4.3
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Functions 3
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Basic FunctionsLecture5.1
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Advanced FunctionsLecture5.2
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Advanced Functions Part 2Lecture5.3
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Dictionaries 3
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Basic DictionariesLecture6.1
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Dictionary FunctionsLecture6.2
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Dictionary Functions 2Lecture6.3
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Assertions 2
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IntroductionLecture7.1
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Assertions and DocstringsLecture7.2
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Classes 3
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Basic ClassesLecture8.1
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Advanced ClassesLecture8.2
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InheritanceLecture8.3
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Matplotlib 2
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PlottingLecture9.1
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Plotting Part 2Lecture9.2
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Advanced List Functions
#If you multiply a list by an integer it will repeat that list that many times
l = [1,2,3,4]
print(l*2)
[1, 2, 3, 4, 1, 2, 3, 4]
List Comprehension¶
List comprehension is a way to apply some sort of logic to all values in a list. For example, if you wanted to multiply all values in a list by 2, this could be achieved with list comprehension. The format of it is that given a list l, you call it like [f(x) for x in l] where f(x) is whatever function you want to apply. In this case, if we wanted to take all values and multiply them by 2, we would say [x*2 for x in l].
#Create and print the basic list
l= [1,2,3,4]
print(l)
#Use list comprehension to multiply all values by 2
l = [x*2 for x in l]
print(l)
[1, 2, 3, 4]
[2, 4, 6, 8]
Modulo Function¶
The modulo function is of the form a%b and returns the remainder if you had divided the number a by b.
#The modulo operator returns the remainder of the left number divided by the right number
print(4%3)
print(7%4)
1
3
Example: Combining the Modulo Function and List Comprehension¶
Let's use both of the things we learned and find the remainder for the numbers 1 through 8 divided by 3.
#Example: Getting the remainder of all numbers in a list divided by 3
l = [1,2,3,4,5,6,7,8]
print([y%3 for y in l])
[1, 2, 0, 1, 2, 0, 1, 2]
We are able to combine an if statement in the list comprehension if we want. The format is:
[f(x) for x in l if condition]
The following code below will return the numbers times 2, but only if the number (before multiplication) is greater than 2.
#Filter the list to be only values above 2 and then multiply each number by two
l = [1,2,3,4]
print(l)
l = [x*2 for x in l if x > 2]
print(l)
[1, 2, 3, 4]
[6, 8]
The Zip Function¶
The zip function takes two lists and iterates through both lists at the same time where the the elements at index 0 in the first and second list are taken, then the elements at index 1, etc.
The format for using the zip function with list comprehension is:
[f(x, y) for x, y in zip(l1, l2)]
The code below shows an example.
#Zip is the way to go through two lists together
l1 = [1,2,3,4,5]
l2 = [10,100,1000,100,10]
print([x*y for x,y in zip(l1,l2)])
[10, 200, 3000, 400, 50]
Nested Lists¶
We can nest lists within lists. In the code below we create a nested list which means that the elements in the list are also lists!
#Many times we use a nested list to represent things
l = [[1,2],[3,4]]
print(l)
[[1, 2], [3, 4]]
If we grab the first element of the list, we will have a list.
#The first index returns the first list
print(l[0])
[1, 2]
We can index a second time to get the value in the list that was nested in the first index.
#This returns the first element of the first list element
print(l[0][0])
1
If we wanted the second element in the second list, we would use [1][1].
#This returns the second element of the second list element
print(l[1][1])
4