Generate variables with consecutive values

user_2041317 0
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I am working with a table with lots of columns. In order not to get magic numbers, I code something like this

colName, colID, colDesc = 1, 2, 3

When I want to add a new item, it becomes

#        vvvvvvvv                           v
colName, colAddr, colID, colDesc = 1, 2 ,3, 4

I add in colAddr where I want it and a 4 at the end. This works with 4 variables but with about 20-30, I get very long lines of code.

So I separated them: one line each

colName = 1
colID = 2
colDesc = 3

If I wish to add something between Name and ID, I would have to renumber the variables which is really painful

colName = 1
colAddr = 2
colID = 3 # renumbered
colDesc = 4 # renumbered

I may have to add columns in between quite often - the table design is still fluid, so I thought of something like this

col = 0
col, colName = col + 1, col
col, colID = col + 1, col
col, colDesc = col + 1, col

If I wanted to add colAddr, then it would just be a one line change

col = 0
col, colName = col + 1, col
col, colAddr = col + 1, col # new line of code
col, colID = col + 1, col
col, colDesc = col + 1, col

This works but looks really messy. Is there a better way of doing this?

enums python
3 Answers

If you use a,b,c=range(3) you can add any number of variables at the beginning and change the range value to match the number of variables.

If numbering needs to start at 1 use range(1,4)

user_34623190

A more elegant solution than the one @depperm suggests is to use enum module (available starting from Python v. 3.4), e.g.:

from enum import Enum
class MyEnum (Enum):
    col, colName, colAddr, colID, colDesc = range(5)

Then you use it in the following way:

MyEnum.col
MyEnum.colName
...

You can of course use non-consequtive values for each of the variables.

user_65739020

You can use collections.namedtuple:

from collections import namedtuple

t = namedtuple('columns', 'colName, colAddr, colID, colDesc')
cols = t._make(range(len(t._fields)))

print(cols)
print(cols.colName)
print(cols.colAddr)
print(cols.colID)
print(cols.colDesc)

Prints:

columns(colName=0, colAddr=1, colID=2, colDesc=3)
0
1
2
3
user_100359850
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