for loops

Lets start with a "for" loop, you can think of this as number of revolutions; if only one number is used such as 10 as a static number it is very limiting.

for elm in range(10):
    res = elm * 2
    print(res)

A for loop using a single variable we are moving forward in being dynamic!

x = 10
for elm in range(x):
    res = elm * 2
    print(res)

Now we start to get crazy by looping through lists and not just a single variable, the range is set by the size of the list so we can by pass its use.

a_group_of_numbers = [ 1,3,7, 9, 12]

for elm in a_group_of_numbers:
    res = elm * 2
    print(res)

And now an iteration through a dictionary, as we do look at the concatenation and casting

a_dictionary = {'x': 1, 'y': 2, 'z': 3}

for key, value in a_dictionary.items():
    value = str(value)
    print(key + " : " + value)

while loops

A while loop will continue to cycle as long as its conditional statement is true. These statements can be hazard to your health, unlike a for loop that has a beginnings and an end, the while loop just goes and goes and goes.

while x < 10:
    print(x)
    x =+ 1

Run the above code, what is the result?

What is the fix for the above code?

What is the condition being set? or not set?

Here is a some real/sudo code, but the idea is for an example of socket listener for a web site with the idea of continuous running while loop.

try:
   s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
except socket.error:
   print 'Failed to create socket'
   sys.exit()
s.bind(host,port)
s.listen(5)
conn_good = 0
while(conn_godd == 0):
    if client.recv() >= 4096:
        conn_good = 1
    elif client.timeout == "extreme":
         conn_good = 1
    else:
      print("keep running")

Moving forward to Lesson 5

Moving back to Lesson 3