[Tutor] Issue w/ while loops

[Danny Yoo]

> Ok, got you!
>
> print("TIME TRACKING")
>
> while True:
>     hours_worked = input("How many hours did you work today? ")
>     try:
>         hours_worked = float(hours_worked)
>         break
>     except ValueError:
>         print ("Invalid input")
> if hours_worked < 24:
>     print("You must be a human.")
> else:
>     print("You must be a cyborg.")
>

Here's an example where naming the while loop might be helpful in making
the code easier to understand.  Or not.  :P  Let's see what this might look
like.  First, let's take the while loop and make it a function:


#########################################################
def GiveMeAGoodName():
    while True:
        hours_worked = input("How many hours did you work today? ")
        try:
            hours_worked = float(hours_worked)
            break
        except ValueError:
            print ("Invalid input")
    return hours_worked

print("TIME TRACKING")
hours_worked = GiveMeAGoodName()
if hours_worked < 24:
    print("You must be a human.")
else:
    print("You must be a cyborg.")
#########################################################

Here, the function-extracting is a little more complex, because there's an
implicit passing of data from one part of the program to the other.  The
loop continues to run till hours_worked is a good float, after which the
rest of the program uses that float.  So that's why the "GiveMeAGoodName"
returns something.


We can look at GiveMeAGoodName(): it's tryingt to get the number of hours
worked.  Let's call it "AskForHoursWorked".


###########################################################
def AskForHoursWorked():
    while True:
        hours_worked = input("How many hours did you work today? ")
        try:
            hours_worked = float(hours_worked)
            break
        except ValueError:
            print ("Invalid input")
    return hours_worked

print("TIME TRACKING")
hours_worked = AskForHoursWorked()
if hours_worked < 24:
    print("You must be a human.")
else:
    print("You must be a cyborg.")
#########################################################


If we have a better feeling for how control flow interacts with functions,
we might simplify the lines in AskForHoursWorked() a little bit.  Here's
one restatement of that function that does the same thing:

#########################################################
def AskForHoursWorked():
    while True:
        hours_worked = input("How many hours did you work today? ")
        try:
            return float(hours_worked)
        except ValueError:
            print ("Invalid input")
#########################################################

I'd argue that this is a little clearer because, in this variation,
hours_worked is now definitely just a string throughout the program's run.
 It doesn't waffle between being a string and being a number.  The function
itself is a little shorter because we can do a "return" to get out of the
function, rather than do the "assign the value, break, then return" that we
had in the original code.


Best of wishes!
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