[sf-lug] [PYCLASS] Still on exercise 2.1

[Charles-Henri Gros]

Christian Einfeldt wrote:
> hi
> 
> On Sat, Oct 4, 2008 at 1:02 AM, Jeffrey Malone <ieatlint at tehinterweb.com
> <mailto:ieatlint at tehinterweb.com>> wrote:
> 
> 
>     /* Set some constants */
> 
> 
> This was wonderfully enlighting to see this problem solved this way.  It
> is elegant, because once the constants have been set, it is possible to
> throw many scenarios at those constants.  Never in a million years would
> I have thought of this myself.  This is excellent instruction, thanks.
> 
> It would seem that it would probably be a good idea to create constants
> in almost every problem, is that correct? 
> 
> Also, it is surprising to me that one would need to define minutes.  You
> would think that the Python programmers would anticipate that people are
> going to need those values and compute with them frequently.
> 
> Also, it would seem that there would need to be a library or a config
> file that one could edit to permanently reflect set values for MIN and
> HOUR.  Are there such files?  Or, to put it another way, where are the
> values for MIN and HOUR stored? In /tmp?  I am assuming those values go
> away when you exit python, is that correct?
>  
> 
>     MIN = 60
>     HOUR = MIN*60
>     easy_pace = 8*MIN+15
>     tempo_pace = 7*MIN+12
>     start_time = 6*HOUR+52*MIN
> 
> 
> Coincidentally, in the law, we have to assign values to works as well in
> the course of written discovery, and there are constantly fights over
> those kinds of things in cases where discovery is hotly disputed, which
> is almost every large civil case.
>  
> 
>     secs = easy_pace * 1 + tempo_pace * 3 + easy_pace * 1
>     print "%d:%02d" % ( (secs/ MIN), (secs%MIN) )
> 
> 
> Since I am still on chapter 2 of the book, we have not covered this kind
> of syntax, which is taken from the print statement above:
> 
> %d:%02d" % ( (secs/ MIN), (secs%MIN) )
> 
> What does the colon denote above there, please?  And is there a name for
> this structure:
> 
> %d:%02d
> 
> And what does the % mean, please?  I am guessing we are going to cover
> that in Chapter 3, so if that is the case, my apologies.  I wanted to
> get my questions out there while I had them in mind. 

%d means: there will be a decimal value to print

%02d means: there will be a decimal value to print; print 2 digits (this
is all a bit too complicated to explain in detail in an e-mail)

The next '%' announces the arguments, i.e. the values referred to above
( a, b ) [where a is (secs/MIN) and b is (secs%MIN) specifies the values

The colon is just printed verbatim.

The (a,b) structure is called a "tuple", it represents multiple values.

For instance to print 3 integers you could use

print "integer 1:%d; integer 2:%d; integer 3:%d" % (11, 12, 13)

This will print:
integer 1:11; integer 2:12; integer 3:13

-- 
Charles-Henri