python - Creating multiple variables

0
votes

I would like to create 10 variables with one for in Python (not an array). Something like this:

for i in range(1,10,1)
    variable i = 100 / i
    print variable i

I want to create variable names, in this case: variable1, variable2, variable3,..., variable10 I don't want an array

I have a map of coordinates (640 x 480). I am identifying the coordinates where the pixel color is white. There are 3 balls in the ground, I would like to get the central coordinate of each ball, so if the coordinate that is been evaluated is close from the last one, the x and y coordinate will be averaged, if the coordinate belongs to a new ball the coordinate belongs to a new group of coordinates will be evaluated.

p=0
h=0
for j in range(1,480,1):
   for i in range(1,640,1):
      c=cv.Get2D(image,j,i)
      if c[0] == 255:
        old_coord X  = new_coord x
        new_coord x += [(i,j)]
        if (old_coord x - 5 < new_coord x < old_coord x + 5)
            averx x = averx x + i
            avery x = averx x + j
            count x = count x + 1
        else
            p = p + 1
            new_coord x += [(i,j)]
average(averx1 , count 1)
average(avery1 , count 1)
average(averx2 , count 2)
average(avery2 , count 2)
2
pythonvariablesfor-loop
No, you don't want to do that. Tell us why, and we'll tell you what you actually want to do. - agf
This is a commonly asked question and it is never the right choice. Why don't you want to use an array (which are usually called lists in Python)? - David Robinson
@Marcin: I take it you have such a language in mind? - David Robinson
If you know the names of the variables in advance, why do you need to create them dynamically? You're going to have to reference them by their actually names afterwards, as well. - martineau
Incidentally, a good blog post on this topic is Keep data out of your variable names - David Robinson

2 Answers

6
votes

you should not do this, but you can if you really want

for j in range(1,10,1):
    exec('var_%d = j'%j)

Can I stress again you should not do this, but I see no reason to hide the ability to hang your self.

Given what you are trying to do, I would look in to morphological operations. There are better algorithms for what you are trying to do. (It looks like what you want to do is already in scipy, examples).

Quoting unutbu:

Maybe I should try to convince you that having variables named variable1, variable2, etc. is a bad idea. Since these variables are numbered, they probably have some close relationship to each other. Perhaps they are all numbers. Suppose you wanted to increment all of them by one. You'd have to write repetitious code such as

variable1 += 1
variable2 += 1
variable3 += 1
... etc

instead of 

for i in range(1,10,1):
    x[i] += 1

Or perhaps you want to feed all those variables into a function. You'd have to write

func(variable1, variable2, variable3, ...)

instead of 

func(**x)

Conclusion: Having numbered variables names is a pain! Save yourself from pain by using a dict or a list.

10
votes

Never create numbered variable names (1 or 2 maybe, but never 9.) Instead use a list or a dict:

x = dict()
for i in range(1,10,1)
    x[i] = 100 / i
    print x[i]

(I used a dict in this case because i starts at 1.) However, depending on how you wish to use x further, you may want to use a list instead.

Maybe I should try to convince you that having variables named variable1, variable2, etc. is a bad idea. Since these variables are numbered, they probably have some close relationship to each other. Perhaps they are all numbers. Suppose you wanted to increment all of them by one. You'd have to write repetitious code such as

variable1 += 1
variable2 += 1
variable3 += 1
... etc

instead of 

for i in range(1,10,1):
    x[i] += 1

Or perhaps you want to feed all those variables into a function. You'd have to write

func(variable1, variable2, variable3, ...)

instead of 

func(**x)

Conclusion: Having numbered variables names is a pain! Save yourself from pain by using a dict or a list.