[Tutor] counting number of inputs (EARLIER VERSION SENT ACCIDENTLY)

[Marc Poulin]

Michelle:

Are you familiar with writing functions?
Here I've created a function named getInputs.

I've also created a few test cases to verify that (a)
my understanding of the problem is correct, and (b) my
solution is correct.

It's important to think about how your program is
supposed to behave in different situations. Do you
think these 3 tests are enough to prove that the code
is correct?

#########################
## start of code       ##
#########################
def getInputs():
    """
    Description:
       Collect numbers entered by the user (up to a
maximum of 5 values) and
       store them in the listOfValues.

       Stop collecting numbers if the user enters -1
or if 5 numbers have been collected.

       If the user entered -1, the -1 is NOT returned
as part of the list.       
    """
    listOfValues = [] ## this list holds the values
entered by the user
    
    for i in range(5):
        newValue = int(raw_input('Enter a number [-1
to exit]:'))
        if newValue == -1:
            # Return right now with whatever is
currently in the list.
            return listOfValues
        else:
            # Add this new value to the list and keep
looping.
            listOfValues.append(newValue)
            
    ## If we got this far, it means the user did not
enter a -1 so
    ## the list contains 5 values.
    return listOfValues

"""
Here are a few test cases to verify the logic of my
code.

Test Case 1:
   INPUTS:
      first entered value: -1
   RESULT:
      function returns empty list

Test Case 2:
   INPUTS:
      first entered value: 1
      second entered value: 2
      third entered value: -1
   RESULT:
      returned list contains [1,2]

Test Case 3:
   INPUTS:
      first entered value: 1
      second entered value: 2
      third entered value: 3
      fourth entered value: 4
      fifth entered value: 5
   RESULT:
      returned list contains [1,2,3,4,5]
"""
if __name__ == "__main__":
    print getInputs()

###################
## end of code   ##
###################


--- Python <python at venix.com> wrote:

> On Wed, 2006-05-03 at 15:33 -0400, MICHELLE EVANS
> wrote:
> > OK, I've tried a different approach to this.
> > How do I get this to stop by using -1?
> > I do not want this to print until either 5 inputs
> have been entered or -1
> > has been entered.  See below:
> > 
> 
> use a "for block" rather than a "while block" to
> have a normal limit of
> 5 repetitions:
> 
> for x in range(5):
> 
> will repeat 5 times with x running from 0 to 4.
> x is ignored - unless some use for it does turn up.
> 
> the break statement allows you to terminate a block,
> so
> 
> 	if number == -1: break
> 
> will end the for block.
> 
> 
> Now, one of the cute features in Python is the else
> clause that goes
> with the for and while blocks.  The else block is
> executed when there is
> no break.  So the skeleton for your program can look
> something like
> 
> for x in range(5):
> 	# get inputs and break on -1
> else:
> 	# no break so just process the inputs
> 
> Good luck.
> 
> > # Add number of per hour
> > numbers = []
> > stop = None
> > while stop != "-1":
> >     number = int(raw_input("Run number(-1 to end)
> : "))
> >     numbers.append(number)
> >     print
> >     for number in numbers:
> >         print number
> > 
> > 
> > 
> > 
> > ----- Original Message ----- 
> > From: "Python" <python at venix.com>
> > To: "MICHELLE EVANS" <evans1018 at verizon.net>
> > Cc: "Tutor Python" <tutor at python.org>
> > Sent: Wednesday, May 03, 2006 12:18 PM
> > Subject: Re: [Tutor] counting number of inputs
> (EARLIER VERSION SENT
> > ACCIDENTLY)
> > 
> > 
> > > (Tip: Best to use reply-to-all when responding
> to an email on the list)
> > > On Tue, 2006-05-02 at 21:34 -0400, MICHELLE
> EVANS wrote:
> > > > number1 = int(raw_input("Run number 1 (-1 to
> end) : "))
> > > > number2 = int(raw_input("Run number 2 (-1 to
> end) : "))
> > > > number3 = int(raw_input("Run number 3 (-1 to
> end) : "))
> > > > number4 = int(raw_input("Run number 4 (-1 to
> end) : "))
> > > > number5 = int(raw_input("Run number 5 (-1 to
> end) : "))
> > > Good.  You collect the string from raw_input and
> convert it to an
> > > integer.
> > >
> > > This will prompt for 5 inputs, but it is missing
> any logic to actually
> > > break if -1 is entered.  With a language like
> BASIC, you could stick in
> > > tests sort of like:
> > > if number1 == -1 goto done:
> > > BUT Python does not have a goto.  So we actually
> need some "flow
> > > control" around the block of code where you
> collect inputs.
> > >
> > > while blocks process an indefinite number of
> times while a test
> > > condition is True.
> > >
> > > for blocks iterate through a sequence until they
> reach the end.  By
> > > providing a sequence with the correct count, you
> can repeat the block
> > > the correct number of times.  The range (and
> xrange for big sequences)
> > > functions provide a sequence of integers that
> can be used conveniently
> > > with for.
> > >
> > > The easiest way to fix your code above would be
> something like:
> > > ask_for_number = True
> > > while ask_for_number:
> > > number1 = ....
> > > if number1 == -1: break
> > > ...
> > > number5 = ...
> > > ask_for_number = False
> > >
> > > HOWEVER, that is not a good approach in the long
> run.
> > >
> > > A better approach is to have a single container
> to hold all of the
> > > inputs.  For this, Python provides lists. 
> Rather than have 5 separate
> > > variables, use a single list variable to hold
> all of the inputs.  Then
> > > use a "for block" to ask for the input and put
> the result into the list.
> > > You already know how to convert the input from a
> string to a number.
> > >
> > > If you have trouble figuring out lists and for
> blocks, ask for help.
> > >
> > > (Sorry about the extra email.  I forgot and used
> ad editor hot-key combo
> > > in my email program which sent the email.)
> > >
> > >
> > > >
> > > >
> > > > # The following will sum the numbers and then
> print the answer
> > > > sum = number1 + number2 + number3 + number4 +
> number5
> > > > print
> > > > print "The total number of parts produced
> was:", sum,"."
> > > >
> > > > I need this to ask the user to enter their
> number per each run.  That is
> > why
> > > > I have 5 different input numbers.  I need this
> break if a -1 is entered.
> > > > Would I use "if-else" to break this if -1 is
> entered?  I need to be able
> > to
> > > > count the number of lines entered.
> > > >
> > > > Thanks
> > > > Rick
> > > >
> > > >
> > > > ----- Original Message ----- 
> > > > From: "Python" <python at venix.com>
> > > > To: "MICHELLE EVANS" <evans1018 at verizon.net>
> > > > Cc: "Tutor Python" <tutor at python.org>
> > > > Sent: Tuesday, May 02, 2006 7:56 PM
> > > > Subject: Re: [Tutor] counting number of inputs
> > > >
> > > >
> > > > > On Tue, 2006-05-02 at 19:25 -0400, MICHELLE
> EVANS wrote:
> > > > > > I am trying to count the number of times a
> positive number is
> > entered
> > > > > > from the user.  But, the program must stop
> after 5 user inputs or a
> > > > > > negative number.
> > > > > >
> > > > > > Can anyone help.
> > > > > Yes, but you need to help yourself also.
> > > > >
> > > > > Do you know how to get input from the user?
> > > > > Do you know how to count things in Python?
> > > > > Do you know how to test a number to see if
> it is positive or negative?
> > > > >
> > > > > Why don't you post your code for any part of
> this problem and explain
> > > > > how it is supposed to work and where you are
> having difficulty.  If
> > > > > necessary, review some of the tutorials to
> get some pointers on
> > writing
> > > > > Python programs.
> > > > >
> > > > > We're happy to help you learn, but do not
> want to simply write your
> > > > > program for you.
> > > > >
> 
=== message truncated ===


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