########## BREAK ##########

#You can break out of a loop any time using the break keyword.

#For example, if you are looking for a particular elemennt

languages = ["Python", "C++", "Java", "Perl", "C#"]

for language in languages:

if language == "Python":

print(language + " found")

break

#Things after break within same block never get hit

#Things outside of the if can still be hit if break is not hit first

for language in languages:

if language == "C++":

print(language + " found")

break

print("YOU CAN'T SEE ME!")

print("It's JOHN CENA!!!!") #executes first iteration but not 2nd

########## CONTINUE #########

#continue works in a similar way except that it will only skip the rest of the iteration.

#This may be useful if you need to continue iterating through the list

#(in this context you could be looking for duplicates or other interesting lanugages)

print("Searching for Java:")

for language in languages:

if language == "Java":

print(language + " found")

continue

print(language + ": Not What we are looking for...")

########## ELSE INSTEAD OF CONTINUE

#This same structure can be achieved with an else

print("Searching for Perl:")

for language in languages:

if language == "Perl":

print(language + " found")

else:

print(language + ": Not What we are looking for...")

########## HOW TO DO NOTHING ##########

for x in range(10):

pass

#You can do this when...uh... hmm.....why WOULD you want to do this?

#My bet is that this is the equivalent to TODO. AKA come back to it later to finish.

#This can also be used for a busy wait... Keeping processor busy.

######### ELSE WITH FOR ##########

#This one is actually new to me. You can use an else with a for.

#This will execute anytime the for loop hits the end of iterable (range or list)

for i in range(0,10):

print(i, end=" ")

else:

print("done")

#This can be useful for a failed search as an example because it will not be hit with break

for language in languages:

if language == "Alabama":

print(language + " found")

break

else:

print("Nope.")

######### While loop ##########

#Another form of loop is the while loop.

#Here is an example that counts 0-9 (including 0 and 9)

i = 0 #initialize

while(i < 10): #condition

print(i, end=" ")

i += 1 #update

print()

#customize the loop as you please! Here's how to count down by two

i = 30

while(i >= 0):

print(i, end=" ")

i -= 2

print()

########## CONVERTING WHILE TO FOR AND BACK ###########

#I think it is important to comfortably work with for and while

#Both loops need an initialization, condition, and update.

initialization = 5

stop_at = 10

increment = 1

for i in range(initialization, stop_at, increment):

print("for loop:", i)

while(initialization < stop_at):

print("while loop:", initialization)

initialization += increment

#To make them match, the update should come at the end of the while

#When passing a variable to range, the variable is not affected

#Range returns new data and initialization is left at 5.

########## ELSE WITH WHILE ##########

#The else statement for a while will execute if no break is hit.

i = 0

while(i < 10):

print(i, end=" ")

i += 1

else:

print("Else of while")

#Random other example

#Checks to see first square >

i = 0

while(i < 10):

if i**2 > 50:

print("First square big enough:", i)

break

i += 1

else:

print("None are big enough")

########## FLAG VARIABLES ##########

#You may not be comfortable with else after a loop

#The equivalent without an else would be like so:

index = -1 #keeps -1 until told otherwise

i = 0

while(i < 10):

if i**2 > 500:

index = i #change index if requirements are met. Not reached because > returns false

break

i += 1

if index > -1:

print("First square big enough:", i)

else:

print("None are big enough")

#Setting a starting value (such as -1), possibly changing it,

#and checking it afterwards creates a flag variable.

#Just a concept. Nothing new on syntax

######### "DO WHILE" loop ##########

#In other languages, there is a concept as a do-while loop.

#These loops always execute at least once.

#We can mimmick this in python easily.

i = 15

print(i) #prints i atleast once no matter what

i += 1

while (i < 10):

print(i)

i += 1

#To generalize this:

#do stuff

#condition - true to continue

#do stuff

#This structure is useful for sentinel / indefinate loops

########## Indefinate / Sentinel loops ##########

#an Indefinate loop is a loop that we do not decide how long it will run ahead of time

#The loop can be stopped, however. This makes it different than an infinate loop.

#An example may be displaying a menu numerous times

print("Do you want to continue? Y/N: ")

response = input()

while response == "Y" or response == "y":

print("Do you want to continue? Y/N: ")

response = input()

#a logical name for the variable would be 'continue' or 'in'

#however these are keyword. don't try it.

#not super common vocab but good to know...

#A sentinel value is a value used to stop a loop. In this case it is anything besides "Y" or "y"

#for programs a sentinel value is often 'q'

########## UPPER AND LOWER ##########

#We can also write our code like so

print("Do you want to continue AGAIN? Y/N: ")

response = input()

while response.lower() == "y":

print("Do you want to continue? Y/N: ")

response = input()

#This is important to understand as "Y" and "y" are not the same thing

#Overlooking this can introduce logical bugs in our software

#There is also an upper.

#We can also invoke it on constant strings

print("am i screaming?".upper())

########## checking if a string is uppercase or lowercase ##########

name = "Caleb"

if name.isupper():

print("Upper")

elif name.islower():

print("Lower")

else:

print("Mixed")

#not sure when you might need this but still good to know.