webinar-for-loops-2022-03-12

# 2022 Mar 12
# WEBINAR: For Loops
# We use loops to repeat actions

# a WHILE loop... btw.. is basically an IF statement
# that repeats as long as its condition is true

# FOR LOOPS are used for repeating actions for every element
# in a container like a list, string, tuple, etc...

# Basic syntax and structure and a FOR LOOP:
# for __ in _someContainer_:
# for _item_ in _someContainer_:
myList = ["Agent Scully", "Agent Mulder", "Walter Skinner", "CSM", "Mr. X"]
for item in myList:
    print(item)

myTuple = ("Gilligan", "Castaway002", "red", "crew")
for item in myTuple:
    print(item)

myString = "Just sit right back and you'll hear a tale."
for char in myString:
    # print(char) # print(char, end="\n")
    print(char, end=" ")
print() # always follow up overriding end with a "regular" print() call
print("hey")

# looping over dictionaries
scoobiesDCT = {
    "Scooby": "a blue collar",
    "Shaggy": "green",
    "Velma": "orange",
    "Daphne": "purple",
    "Fred": "an ascot"
}
# myDictionary[someKey] --> retrieve the value for that key
# myDictionary[someKey] = value
for key in scoobiesDCT: # key, k... those are good for loop vars for a dictionary
    # value = scoobiesDCT[key]
    print("{} wears {}.".format(key, scoobiesDCT[key]))

# myVar = input().rstrip()
# if myVar in myDictionary: # is this key even in this dictionary?

for k, v in scoobiesDCT.items(): # key, value
    # print("{} always wears {}.".format(k, v))
    print(scoobiesDCT[k]) # print(v)

print(scoobiesDCT.values())

# How do we repeat just "some number" of times?
# for n in 5: # can't do this! Integers are not iterable
for n in range(0, 5):
    print(n)

# looping over a list or other container and you want the INDEX
# loop over the range() of the len()
for i in range(0, len(myList)):
    print("{}: {}".format(i, myList[i]))
for i in range(0, len(myList)):
    if i < len(myList) - 1: # not the last one
        print("{} ->".format(myList[i]), end=" ")
    else: # so... the last one
        print(myList[i])
# we could use str join() to do the same thing
print("-->".join(myList))

# question on delimiter strings... could be literal or variable
myDelim = "   "
print(myDelim.join(myList))

# Advanced... Ch 13 and after
# We use for loops when looping over line by line data from files...
# I have a CSV file named "mock_data.csv"
with open("mock_data.csv", "r") as f:
    # read() --> returns whole file as one big str
    # readlines() --> returns you a line by line list of strings
    # for line in f: # but I like known container types...
    contents = f.readlines()
# print(contents)
for line in contents:
    line = line.rstrip()
    print(line) # end="\n"
    lineList = line.split(",")
    print(lineList)
    print("{} is using IP {}".format(lineList[3], lineList[4]))

# help() and dir() are always your friends, and work great in the exam:
help(str)
help(list)
print(dir(dict))
help(dict.get) # use dir() to zero in on a specific method or property

# question on whitespace characters
# use strip() or rstrip() to remove from input strings
myVar = input().rstrip() # " ", "\n", "\r", "\f", "\t", plus other Unicode space variations
myVar = int(input().rstrip())