Programming Forums > Script Programming > Python

arod199113 · Feb 25th, 2005, 1:49 PM

i was doing a tutorial a while ago and got stuck on the following part
i never finished the tutorial because i never understood the purpose for this:

(Toggle Plain Text)

a = 23
b = -23

def my_abs(num):
    if num < 0:
        num = -num
    return num

if my_abs(a) == my_abs(b):
    print "The absolute values of", a,"and",b,"are equal"
else:
    print "The absolute values of a and b are different"

they said that was simpler than typing this:

(Toggle Plain Text)

a = 23
b = -23

if a < 0:
    a = -a

if b < 0:
    b = -b

if a == b:
    print "The absolute values of", a,"and",b,"are equal"
else:
    print "The absolute values of a and b are different"

i dont understand what "def" does.
i understand that the "my_abs" is just a variable and can have another name
same with "(num)"
but i dont understand the

(Toggle Plain Text)

if my_abs(a) == my_abs(b):

part

Fred · Feb 25th, 2005, 5:40 PM

The 'def' statement defines a so called function. You define it, and then you can use it with whichever numbers you want.

(Toggle Plain Text)

def my_abs(num): #num is a placeholder, so you can put in whichever 
    if num < 0:                           number you like
        num = -num
    return num

(Toggle Plain Text)

if my_abs(a) == my_abs(b):

This simply 'calls' the function. Meaning, that it is applied with the value of 'a', and then with the value of 'b' --> those were assigned to +-23.
my_abs(a) simply replaces every 'num' in the function with a 23, and then returns that value, so it can be compared to the absolute value of 'b', which is determined the same way.
I hope this helped a bit...

arod199113 · Feb 28th, 2005, 6:06 PM

where it sais (num) "num" can be anything?

Ooble · Mar 1st, 2005, 4:23 PM

It can. I would advise only sending numbers though.

arod199113 · Mar 1st, 2005, 6:42 PM

if you looked in the beginning of this thread i said that the tutorial said that the second way was easier
to me the first one is easier even if it takes up more space(since when do we worry about space saving these days anyway?)
but in other programs is "def" necessary?

Fred · Mar 1st, 2005, 7:59 PM

Quote:

Originally Posted by arod199113

in other programs is "def" necessary?

Well, it is all about code reuse...
It is not necessary, but it sure makes the job easier. For example, if you did not use a def statement to define the absolute value function, you would have to type the whole thing every time you want two numbers compared by their absolute value. It is not about space saving, but about time saving...

arod199113 · Mar 2nd, 2005, 5:28 AM

i have all the time in the world
if eventualy i want to do it quicker than i will learn it
thanks thats all i realy needed to know

block01cube · Mar 2nd, 2005, 9:29 AM

It isn't just a matter of code reuse. If you want to harness the full object oriented power of python you will need to learn about methods and classes.

But for small programs or scripts you could get by without using def (though it would help you even then).

Cheers,

b01c

Dietrich · Mar 3rd, 2005, 11:01 AM

By using the right function names you can make your code more readable too. Take a look at this ...
[PHP]# a quick look at Python functions

def PieCookingStatus(CookingTime):
if CookingTime < 30:
print "Still cooking!"
elif CookingTime <= 40:
print "Almost done!"
else:
print "Take pie out of the oven!"

def PiePercentCooked(CookingTime):
return 100*CookingTime/40

# check the apple pie in the oven after 30 minutes
PieCookingStatus(30)
print "Pie is %d percent cooked." % PiePercentCooked(30);
[/PHP]

arod199113 · Mar 3rd, 2005, 2:03 PM

so "def" gives another name to a variable?

Feb 25th, 2005, 1:49 PM	#1
arod199113 Programmer Join Date: Feb 2005 Posts: 86 Rep Power: 0	def my_abs()? i was doing a tutorial a while ago and got stuck on the following part i never finished the tutorial because i never understood the purpose for this: (Toggle Plain Text) a = 23 b = -23 def my_abs(num): if num < 0: num = -num return num if my_abs(a) == my_abs(b): print "The absolute values of", a,"and",b,"are equal" else: print "The absolute values of a and b are different" a = 23 b = -23 def my_abs(num): if num < 0: num = -num return num if my_abs(a) == my_abs(b): print "The absolute values of", a,"and",b,"are equal" else: print "The absolute values of a and b are different" they said that was simpler than typing this: (Toggle Plain Text) a = 23 b = -23 if a < 0: a = -a if b < 0: b = -b if a == b: print "The absolute values of", a,"and",b,"are equal" else: print "The absolute values of a and b are different" a = 23 b = -23 if a < 0: a = -a if b < 0: b = -b if a == b: print "The absolute values of", a,"and",b,"are equal" else: print "The absolute values of a and b are different" i dont understand what "def" does. i understand that the "my_abs" is just a variable and can have another name same with "(num)" but i dont understand the (Toggle Plain Text) if my_abs(a) == my_abs(b): if my_abs(a) == my_abs(b): part

Feb 25th, 2005, 5:40 PM	#2
Fred Programmer Join Date: Feb 2005 Posts: 67 Rep Power: 4	The 'def' statement defines a so called function. You define it, and then you can use it with whichever numbers you want. (Toggle Plain Text) def my_abs(num): #num is a placeholder, so you can put in whichever if num < 0: number you like num = -num return num def my_abs(num): #num is a placeholder, so you can put in whichever if num < 0: number you like num = -num return num (Toggle Plain Text) if my_abs(a) == my_abs(b): if my_abs(a) == my_abs(b): This simply 'calls' the function. Meaning, that it is applied with the value of 'a', and then with the value of 'b' --> those were assigned to +-23. my_abs(a) simply replaces every 'num' in the function with a 23, and then returns that value, so it can be compared to the absolute value of 'b', which is determined the same way. I hope this helped a bit...

Mar 1st, 2005, 4:23 PM	#4
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	It can. I would advise only sending numbers though. __________________ Me :: You :: Them

Mar 3rd, 2005, 11:01 AM	#9
Dietrich Professional Programmer Join Date: Feb 2005 Posts: 434 Rep Power: 4	By using the right function names you can make your code more readable too. Take a look at this ... [PHP]# a quick look at Python functions def PieCookingStatus(CookingTime): if CookingTime < 30: print "Still cooking!" elif CookingTime <= 40: print "Almost done!" else: print "Take pie out of the oven!" def PiePercentCooked(CookingTime): return 100*CookingTime/40 # check the apple pie in the oven after 30 minutes PieCookingStatus(30) print "Pie is %d percent cooked." % PiePercentCooked(30); [/PHP] __________________ I looked it up on the Intergnats!

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Feb 28th, 2005, 6:06 PM	#3
arod199113 Programmer Join Date: Feb 2005 Posts: 86 Rep Power: 0	where it sais (num) "num" can be anything?

Mar 1st, 2005, 6:42 PM	#5
arod199113 Programmer Join Date: Feb 2005 Posts: 86 Rep Power: 0	if you looked in the beginning of this thread i said that the tutorial said that the second way was easier to me the first one is easier even if it takes up more space(since when do we worry about space saving these days anyway?) but in other programs is "def" necessary?

Mar 2nd, 2005, 5:28 AM	#7
arod199113 Programmer Join Date: Feb 2005 Posts: 86 Rep Power: 0	i have all the time in the world if eventualy i want to do it quicker than i will learn it thanks thats all i realy needed to know

Mar 2nd, 2005, 9:29 AM	#8
block01cube Newbie Join Date: Feb 2005 Posts: 10 Rep Power: 0	It isn't just a matter of code reuse. If you want to harness the full object oriented power of python you will need to learn about methods and classes. But for small programs or scripts you could get by without using def (though it would help you even then). Cheers, b01c

Mar 3rd, 2005, 2:03 PM	#10
arod199113 Programmer Join Date: Feb 2005 Posts: 86 Rep Power: 0	so "def" gives another name to a variable?

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Programming Forums > Script Programming > Python

def my_abs()?