[NeilHanlon]

If I had to guess (Since I don't know python), it'd be that you might have to convert the raw input to a string/integer or something.

[Koregg]

Yeah I thought so too, but I tried it and couldn't get it to work :/ Thanks though!

[Sephern]

The issue is that you're comparing things of a different type.

raw_input

gives back a string, so you're comparing a string to an integer. That'll always return false.

In essence what you're doing is

"9" == 9

If you run that past a python interpreter you'll find that it's always false.

You have 2 options. The first is that you could convert your input into an integer. The issue with this is that it'll throw an exception if it can't convert properly (i.e. if I put "hello" into your input, there's no way of making that a number). You could catch this exception and handle it appropriately (in fact, that's probably what you'd do in most situations) but here it seems that you'd just want normal strings to be handled like any other invalid input.

You could, therefore, turn the ints on the right hand side of your comparison into string literals instead.

if yn == "9":

[NeilHanlon]

Sephern, on 11 August 2012 - 10:10 AM, said:

The issue is that you're comparing things of a different type.

raw_input

gives back a string, so you're comparing a string to an integer. That'll always return false.

In essence what you're doing is

"9" == 9

If you run that past a python interpreter you'll find that it's always false.

You have 2 options. The first is that you could convert your input into an integer. The issue with this is that it'll throw an exception if it can't convert properly (i.e. if I put "hello" into your input, there's no way of making that a number). You could catch this exception and handle it appropriately (in fact, that's probably what you'd do in most situations) but here it seems that you'd just want normal strings to be handled like any other invalid input.

You could, therefore, turn the ints on the right hand side of your comparison into string literals instead

if yn == "9":

Purely as a learning experience, does Python not have the same difference most languages have between == and === (Where == doesn't check type, and === does)?

[Sephern]

NeilHanlon, on 11 August 2012 - 10:23 AM, said:

Purely as a learning experience, does Python not have the same difference most languages have between == and === (Where == doesn't check type, and === does)?

No. Python is a strongly typed language, so you have to cast/convert between types (it'd make no sense to have a triple equals).

[callumacrae]

The double equals operator in loosely typed languages is a silly operator: it promotes excessive laziness and can create some just plain weird behaviour.

[Ruku]

callumacrae, on 11 August 2012 - 10:54 AM, said:

The double equals operator in loosely typed languages is a silly operator: it promotes excessive laziness and can create some just plain weird behaviour.

I've never actually given this much thought, but I agree on the grounds that it's easier to read code where the type conversions are explicit. That said, weird behaviour tends to stem from misunderstanding, especially amongst new and inexperienced programmers. I very rarely see

===

appear in even the most established, commercially-backed PHP projects, for instance.

[TheEmpty]

the

===

is equal to

&one == &two

in terms of C right? In ruby you can compare object ids instead, what would be the PHP alt? Or better yet, Python alt.

[Lemon]

TheEmpty, on 11 August 2012 - 01:42 PM, said:

the

===

is equal to

&one == &two

in terms of C right? In ruby you can compare object ids instead, what would be the PHP alt? Or better yet, Python alt.

Not quite, as they could be different addresses in memory but they just to have the same value and type; for == you just need same casted value but not necessarily the same type. If you're thinking in terms of C, === would be like an equality in which there is no cast (i.e same types) but the pointers are not necessarily the same. From the PHP manual:

$a == $b -> "TRUE if $a is equal to $b after type juggling."
$a === $b -> "TRUE if $a is equal to $b, and they are of the same type."

Edit: Oh, Python topic so this is not really particularly useful

[lobabob]

Quote

Not quite, as they could be different addresses in memory but they just to have the same value and type; for == you just need same casted value but not necessarily the same type. If you're thinking in terms of C, === would be like an equality in which there is no cast (i.e same types) but the pointers are not necessarily the same. From the PHP manual:

$a == $b -> "TRUE if $a is equal to $b after type juggling."
$a === $b -> "TRUE if $a is equal to $b, and they are of the same type."

.........I finally know what === means

[TheMaster]

Lemon, on 11 August 2012 - 02:03 PM, said:

$a == $b -> "TRUE if $a is equal to $b after type juggling."
$a === $b -> "TRUE if $a is equal to $b, and they are of the same type."

This should be put in programming guides from now on

[callumacrae]

It has too many crazy side effects.

"032" == "32"
"032" == 32
032 != 32

"\n \t \r" == 0

[Lemon]

TheMaster, on 11 August 2012 - 11:06 PM, said:

This should be put in programming guides from now on

It already is, I just took that from the php manual.