pythonpython-3.xstringlistrange

# Convert range(r) to list of strings of length 2 in python

I just want to change a list (that I make using range(r)) to a list of strings, but if the length of the string is 1, tack a 0 on the front. I know how to turn the list into strings using

``````ranger= map(str,range(r))
``````

but I want to be able to also change the length of those strings.

Input:

``````r = 12
ranger = range(r)
ranger = magic_function(ranger)
``````

Output:

``````print ranger
>>> ['00','01','02','03','04','05','06','07','08','09','10','11']
``````

And if possible, my final goal is this: I have a matrix of the form

``````numpy.array([[1,2,3],[4,5,6],[7,8,9]])
``````

and I want to make a set of strings such that the first 2 characters are the row, the second two are the column and the third two are '01', and have matrix[row,col] of each one of these. so the above values would look like such:

``````000001    since matrix[0,0] = 1
000101    since matrix[0,1] = 2
000101    since matrix[0,1] = 2
000201
000201
000201
etc
``````

Solution

• Use `string formatting` and list comprehension:

``````>>> lst = range(11)
>>> ["{:02d}".format(x) for x in lst]
['00', '01', '02', '03', '04', '05', '06', '07', '08', '09', '10']
``````
``````>>> [format(x, '02d') for x in lst]
['00', '01', '02', '03', '04', '05', '06', '07', '08', '09', '10']
``````