Re: [Tutor] x%2
bob gailer wrote: On 1/10/2012 1:47 PM, Noah Hall wrote: a % b is the remainder operator. It returns what's "left" after dividing a by b. Not to beat a dead horse- but % is the modulo operator. That depends on how you define "remainder" and "modulo". There is no definition agreed on by all people, and so we get into terminology disputes. To a mathematician, "modulo operator" is meaningless. Modulo is a modifier to a statement, not an operator, and is written "mod" as in: 1 = 5*3 mod 7 It returns the residue class of the 2 operands. When a is positive this is the same as remainder, but not so for negative a. "Remainder" is ambiguous for negative values. -7/5 could be given as -1 with -2 remainder, or as -2 with 3 remainder. One might define a remainder operation as returning a result: - which is always positive - with the sign of the divisor - with the sign of the dividend - which is closest to zero - which is furthest away from zero The last two require further variations, depending on how you resolve ties. One might also define i%0 to be i, or as undefined. So by my count, there are at least 18 consistent ways to define a remainder/modulo operator. A very few languages define two operators, or functions, e.g. Ada defines a rem operator which returns the remainder with the sign of the dividend and a mod operator which returns the remainder with the sign of the operator. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] x%2
On 1/10/2012 1:47 PM, Noah Hall wrote: a % b is the remainder operator. It returns what's "left" after dividing a by b. Not to beat a dead horse- but % is the modulo operator. It returns the residue class of the 2 operands. When a is positive this is the same as remainder, but not so for negative a. >>> 5%3 2 >>> -5%3 1 >>> FWIW the Python documentation (at least as of 2.7.2 has this wrong!) -- Bob Gailer 919-636-4239 Chapel Hill NC ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] x%2
On Tue, Jan 10, 2012 at 1:47 PM, Noah Hall wrote:
> On Tue, Jan 10, 2012 at 6:24 PM, emin wrote:
>> answers = ["yes","no"]
>> reaction = ["OK.I GOT IT.But why symbol of percent % not symbol of division
>> / ?","PLEASE EXPLAIN MORE"]
>>
>> print "1st SORRY FOR BAD ENGLISH & DISTURBING:((i am beginner)"
>> print "So you want to say it doesnt mean 2 percent of x and it means x
>> divisible by 2?"
>> print "Yes"
>> print "or"
>> print "No"
>> answerChoise = raw_input("Type here: ")
>>
>> if answerChoise == "yes" or answerChoise == "Yes":
>> print reaction[0]
>>
>> elif answerChoise == "no" or answerChoise == "No":
>> print reaction[1]
>
> Urm, yeah, while this is cute and all, it's not a great way of asking
> a question.
>
> I'm not totally sure what you mean, so I'm just going to say -
>
> a / b is the division operator. It divides things. It returns a divided by b.
> a % b is the remainder operator. It returns what's "left" after dividing a by
> b.
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--
The / operator signifies division. The % signifies modulo. see this:
http://en.wikipedia.org/wiki/Modulo_operation
and see this: http://docs.python.org/reference/expressions.html#index-998
Joel Goldstick
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Re: [Tutor] x%2
On Tue, Jan 10, 2012 at 6:24 PM, emin wrote:
> answers = ["yes","no"]
> reaction = ["OK.I GOT IT.But why symbol of percent % not symbol of division
> / ?","PLEASE EXPLAIN MORE"]
>
> print "1st SORRY FOR BAD ENGLISH & DISTURBING:((i am beginner)"
> print "So you want to say it doesnt mean 2 percent of x and it means x
> divisible by 2?"
> print "Yes"
> print "or"
> print "No"
> answerChoise = raw_input("Type here: ")
>
> if answerChoise == "yes" or answerChoise == "Yes":
> print reaction[0]
>
> elif answerChoise == "no" or answerChoise == "No":
> print reaction[1]
Urm, yeah, while this is cute and all, it's not a great way of asking
a question.
I'm not totally sure what you mean, so I'm just going to say -
a / b is the division operator. It divides things. It returns a divided by b.
a % b is the remainder operator. It returns what's "left" after dividing a by b.
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Re: [Tutor] x%2
emin wrote:
http://www.youtube.com/watch?src_vid=QaYAOR4Jq2E&feature=iv&annotation_id=annotation_149056&v=M3g1GEkmyrw
in this tutorial what does mean x%2 ?
x % 2 gives the remainder when you divide x by 2.
i think: i * 2% = always even number
What does that mean? i*2% does not work in Python. In Python, % does not mean
percentage and so you can't multiply by 2%.
I guess you mean
i % 2 == 0 means i is an even number
and this would be correct. If i % 2 == 0 then i is even. If it equals 1 then i
is odd.
but why not 4,6 or 8? but i * 4(6,8,10,12...)% = always even number too
The remainder i % n will be a number between 0 and n-1. i%2 is useful because
there are only two possible results, 0 (i is even) or 1 (i is odd).
i%4 is less useful, because there are four possibilities:
0 (i is even)
1 (i is odd)
2 (i is even)
3 (i is odd)
i%10 is less useful still, because there are ten possibilities:
0,2,4,6,8: i is even
1,3,5,7,9: i is odd
for example: 100 * 2(4,6,8,10,12...)% = 2(4,6,8,10,12...)
even numbers = {2,4,6,8,10,12...}
I don't understand what you are trying to say here.
and how pyton understanding 0(even or odd number or it is an exception?)?
0 is always an even number, because it has 0 remainder when you divide by 2.
--
Steven
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Re: [Tutor] x%2
2012/1/8 emin :
> http://www.youtube.com/watch?src_vid=QaYAOR4Jq2E&feature=iv&annotation_id=annotation_149056&v=M3g1GEkmyrw
> in this tutorial what does mean x%2 ?
> i think: i * 2% = always even number
> but why not 4,6 or 8? but i * 4(6,8,10,12...)% = always even number too
> for example: 100 * 2(4,6,8,10,12...)% = 2(4,6,8,10,12...)
> even numbers = {2,4,6,8,10,12...}
> and how pyton understanding 0(even or odd number or it is an exception?)?
While it is true that all numbers divisible by 4 are even, not all
even numbers are divisible by 4. All even numbers, however, are
divisible by 2.
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