Title
Lists and Dictionaries (In-Class) Variables all have a type: String, Integer, Float, List and Dictionary are some key types. In Python, variables are given a type at assignment, Types are important to understand and will impact operations, as we saw when we were required to user str() function in concatenation.
print("What is the variable name/key?", "value?", "type?", "primitive or collection, why?")
name = "Luke Riggins"
print("name", name, type(name))
print()
# variable of type integer
print("What is the variable name/key?", "value?", "type?", "primitive or collection, why?")
age = 17
print("age", age, type(age))
print()
# variable of type float
print("What is the variable name/key?", "value?", "type?", "primitive or collection, why?")
score = 90.0
print("score", score, type(score))
print()
# variable of type list (many values in one variable)
print("What is variable name/key?", "value?", "type?", "primitive or collection?")
print("What is different about the list output?")
langs = ["Python", "JavaScript", "Java", "Bash"] # *I added bash as a language*
print("langs", langs, type(langs), "length", len(langs))
print("- langs[3]", langs[3], type(langs[3])) # *I changed the index from 0 to 3 so that the print command will print Bash instead of Python*
print()
# variable of type dictionary (a group of keys and values)
print("What is the variable name/key?", "value?", "type?", "primitive or collection, why?")
print("What is different about the dictionary output?")
person = {
"name": name,
"age": age,
"score": score,
"langs": langs
}
print("person", person, type(person), "length", len(person))
print('- person["name"]', person["name"], type(person["name"]))
InfoDb = []
# InfoDB is a data structure with expected Keys and Values
# Append to List a Dictionary of key/values related to a person and cars
InfoDb.append({
"FirstName": "John",
"LastName": "Mortensen",
"DOB": "October 21",
"Residence": "San Diego",
"Email": "jmortensen@powayusd.com",
"Owns_Cars": ["2015-Fusion", "2011-Ranger", "2003-Excursion", "1997-F350", "1969-Cadillac"]
})
# Append to List a 2nd Dictionary of key/values
InfoDb.append({
"FirstName": "Luke",
"LastName": "Riggins",
"DOB": "December 2",
"Residence": "San Diego",
"Email": "luker56233@powayusd.com",
"Owns_Cars": ["Volkswagon Passat"]
})
# PUTTING MY INFORMATION (HACK!)
InfoDb.append({
"FirstName": "Luke",
"LastName": "Riggins",
"DOB": "December 2",
"Residence": "Rancho Bernardo",
"Email": "luke120204@gmail.com",
"Owns_Cars": ["Toyota"]
})
# PUTTING MY PARTER'S INFORMATION (HACK!)
InfoDb.append({
"FirstName": "Jeffery",
"LastName": "Lee",
"DOB": "December 27",
"Residence": "4S Ranch",
"Email": "jefferyl56783@stu.powayusd.com",
"Owns_Cars": ["Honda Accord"]
})
# Print the data structure
print(InfoDb)
Formatted output of List/Dictionary - for loop Managing data in Lists and Dictionaries is for the convenience of passing the data across the internet, to applications, or preparing it to be stored into a database. It is a great way to exchange data between programs and programmers. Exchange of data between programs includes the data type the method/function and the format of the data type. These concepts are key to learning how to write functions, receive, and return data. This process is often referred to as an Application Programming Interface (API).
Next, we will take the stored data and output it within our notebook. There are multiple steps to this process...
Preparing a function to format the data, the print_data() function receives a parameter called "d_rec" short for dictionary record. It then references different keys within [] square brackets. Preparing a function to iterate through the list, the for_loop() function uses an enhanced for loop that pull record by record out of InfoDb until the list is empty. Each time through the loop it call print_data(record), which passes the dictionary record to that function. Finally, you need to activate your function with the call to the defined function for_loop(). Functions are defined, not activated until they are called. By placing for_loop() at the left margin the function is activated.
def print_data(d_rec):
print(d_rec["FirstName"], d_rec["LastName"]) # using comma puts space between values
print("\t", "Residence:", d_rec["Residence"]) # \t is a tab indent
print("\t", "Birth Day:", d_rec["DOB"])
print("\t", "Cars: ", end="") # end="" make sure no return occurs
print(", ".join(d_rec["Owns_Cars"])) # join allows printing a string list with separator
print()
# for loop algorithm iterates on length of InfoDb
def for_loop():
print("For loop output\n")
for record in InfoDb:
print_data(record)
for_loop()
Formatted output of List/Dictionary - for loop
Prepare a function to format the data
Prepare a function to iterate through the list
Activate your function
def print_data(d_rec):
print(d_rec["FirstName"], d_rec["LastName"]) # using comma puts space between values
print("\t", "Residence:", d_rec["Residence"]) # \t is a tab indent
print("\t", "Birth Day:", d_rec["DOB"])
print("\t", "Cars: ", end="") # end="" make sure no return occurs
print(", ".join(d_rec["Owns_Cars"])) # join allows printing a string list with separator
print()
# for loop algorithm iterates on length of InfoDb
def for_loop():
print("For loop output\n")
for record in InfoDb:
print_data(record)
for_loop()
Alternate methods for iteration - while loop
The while_loop() function contains a while loop, "while i < len(InfoDb):". This counts through the elements in the list start at zero, and passes the record to print_data()
def while_loop():
print("While loop output\n")
i = 0
while i < len(InfoDb):
record = InfoDb[i]
print_data(record)
i += 1
return
while_loop()
Recursion
recursive_loop(i) function is primed with the value 0 on its activation with "recursive_loop(0)"
ultimately the "if i < len(InfoDb):" will evaluate to false and the program ends
def recursive_loop(i):
if i < len(InfoDb):
record = InfoDb[i]
print_data(record)
recursive_loop(i + 1)
return
print("Recursive loop output\n")
recursive_loop(0)
Creating a For Loop with Index
for indx, record in enumerate(InfoDb):
print("Record #" + str(indx+1) + ": ", end = "")
print_data(record)
Reverse Order
for record in reversed(InfoDb):
print_data(record)