LAST NAME, FIRST NAME
R00000000
ENGR 1330 Laboratory 4.1 - In-Lab
# Preamble script block to identify host, user, and kernel
import sys
! hostname
! whoami
print(sys.executable)
print(sys.version)
print(sys.version_info)
A list is a collection of data that are somehow related. It is a convenient way to refer to a collection of similar things by a single name, and using an index (like a subscript in math) to identify a particular item.
In engineering and data science we use lists a lot - we often call them vectors, arrays, matrices and such, but they are ultimately just lists.
To declare a list you can write the list name and assign it values. The square brackets are used to identify that the variable is a list. Like:
MyList = [7,11,5,9,13,66,99,223]
One can also declare a null list and use the append() method to fill it as needed.
MyOtherList = [ ]
Python indices start at ZERO. Alot of other lnguages start at ONE. Its just the convention.
The first element in a list has an index of 0, the second an index of 1, and so on. We access the contents of a list by referring to its name and index. For example
MyList[3] has a value of the number 9.MyOtherList = [] #Create an empty list
print(MyOtherList)
MyOtherList.append(765) #Add one item to the list
print(MyOtherList)
MyList = [7,11,5,9,13,66,99,223] #Define a list
print(MyList)
sublist = MyList[3:6] #slice a sublist
print("sublist is: ", sublist)
mysum = sum(sublist) #sum the numbers in the sublist
print("Sum: ", mysum)
mylength = len(sublist) #get the length of the sublist
print("Length: ", mylength)
A tuple is a special kind of list where the values cannot be changed after the list is created. It is useful for list-like things that are static - like days in a week, or months of a year. You declare a tuple like a list, except use round brackets instead of square brackets.
MyTupleName = ("Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec")
A dictionary is a special kind of list where the items are related data PAIRS. The second item could itself be a list, so a dictionary would be a meaningful way to build a database in Python.
To declare a dictionary using curly brackets
MyPetsNamesAndMass = { "Dusty":7.8 , "Aspen":6.3, "Merrimee":0.03}
To declare a dictionary using the dict() method
MyPetsNamesAndMassToo = dict(Dusty = 7.8 , Aspen = 6.3, Merrimee = 0.03)
Some examples follow:
MyTupleName = ("Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec")
print(MyTupleName)
MyPetsNamesAndMass = { "Dusty":7.8 , "Aspen":6.3, "Merrimee":0.03}
print(MyPetsNamesAndMass)
MyPetsNamesAndMassToo = dict(Dusty = 7.8 , Aspen = 6.3, Merrimee = 0.04)
print(MyPetsNamesAndMassToo)
# Tuples
MyTupleName = ("Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec")
# Access a Tuple
print ("5th element of the tuple:", MyTupleName[4])
# Dictionary
MyPetsNamesAndMass = { "Dusty":7.8 , "Aspen":6.3, "Merrimee":0.03}
# Access the Dictionary
print ("Aspen's mass = ", MyPetsNamesAndMass["Aspen"])
# Change a value in a dictionary
print ("Merrimee's mass" , MyPetsNamesAndMass["Merrimee"])
MyPetsNamesAndMass["Merrimee"] = 0.01
print ("Merrimee's mass" , MyPetsNamesAndMass["Merrimee"], "She lost weight !")
# Alternate dictionary
MyPetsNamesAndMassToo = dict(Dusty = 7.8 , Aspen = 6.3, Merrimee = 0.03)
print ("Merrimee's mass" , MyPetsNamesAndMassToo["Merrimee"])
# Attempt to change a Tuple
#MyTupleName[3]=("Fred") # Activate this line and see what happens!
FD = {"Quentin":"Tarantino","2020":[2020,"COVID",19,"Pandemic"],"Bond":["James","Gun",("Paris","Tokyo","London")]} #A nested dictionary
print(FD)
FD['2020'][3]
FD['Bond'][2][1]
FD['Bond']
FD['Bond'][2]
FD['Bond'][2][0]
Here are some great reads on this topic:
Here are some great videos on these topics: