Quick question from a super noob.

[SIXAXIS]

Hi,

As you can see, I'm extremely new to Python, and although it's not the first language that I'm learning to program in, I don't know how to do anything. My question is: How do you make a variable a real number instead of an integer?

[Nick]

instead of assigning 10 to the variable foo let's call it, try assigning 10.0

[McKenzie]

Right, unless your problem is something like:

code:

n = input("Enter numerator: ") d = input("Enter denominator: ") print "that is", n / d

in which case you need to use float if you want a decimal answer, like:

code:

print "that is", float(n) / d

Keep in mind that Python is dynamically typed so:

code:

x = 12 x = 4.5 x = "Dog"

works just fine.

[Sniper4Life]

mckenzie...how would u set it so that the decimals can only go SO FAR...like you can only have 4 or 3 decimals...or only 1...??????

[[Gandalf]]

Well, I'm not McKenzie, however...

code:

>>> print "Amount: %.2f" % (3.141592653589)  Amount: 3.14

[Sniper4Life]

so....%2f should do it?

oh ya i tried your thing and it works
ty
but u cant use it if you do firstpx-secondpx as what your gonna round

code:

firstpx=input ("First point's x coordinate: ") firstpy=input ("First point's y coordinate: ") print " " secondpx=input ("Second point's x coordinate: ") secondpy=input ("Second point's y coordinate: ") print " " print "First point:  ","(","%.2f" % firstpx,",","%.2f" % firstpy,")" print "Second point: ","(","%.2f" % secondpx,",","%.2f" % secondpy,")" print " " print "Distance: ""(",firstpx-secondpx,",",firstpy-secondpy,")"

k ive been stuck on this code like forever cus i dont know how to round it....at the last line when you print distance...how can u make it so you can round it?
since its printing an operation...i dont kno...how to round it...O.O

[Sniper4Life]

nvr mind i just figured it out its very simple ^^
i nvr learned bout floats in python so it was a bit confusing for me...

code:

x=float(firstpx-secondpx) y=float(firstpy-secondpy) print "Distance: ""(","%.2f" % x,",","%.2f" % x,")"

ya that solves my problem ^^
(ps-awesome im not a noob programmer any more )

[Zeroth]

Be very, very, very careful with using input. Its basically evaluating all input typed by the user. So one could feasibly use straight python code, write a function, or manipulate the program state via input.

Your usage of input means that the user could input either an int or a float. You need to use float(firstpx) to force them to floats.

Second of all, its much nicer to use:

code:

print "First point: (%.2f,%.2f)" % (float(firstpx), float(firstpy))

The use of the brackets around the two arguments creates a tuple, which python automatically unpacks to the positional arguments in the string.

You can also do some really cool stuff like this:

code:

>>> d = {'car': 'haha', 'cdr': '!lisp'} >>> print "%(car)s" % d haha >>>

What happened there is that the key is inside the ()'s, and the format is right after, the s. By passing a dict, you can fill in the string as necessary, so long as empty keys still have a value(ideally, just a blank string ""). Of course, any class that behaves like a dict will work here too .

[wtd]

Sniper4Life @ Mon Apr 13, 2009 11:40 am wrote:

mckenzie...how would u set it so that the decimals can only go SO FAR...like you can only have 4 or 3 decimals...or only 1...??????

Keep in mind that you can't control the accuracy of the information stored as a floating point number. You can only control the accuracy of the output.

[Sniper4Life]

ya wtd thats what i meant
for question introEx5 on mckenzie's exercises i need to control the output...