replacing numbers in LARGE MATRIX with criterium in 2 columns (a--> b)

[MRAB]

Alexzive wrote:
> Hello,
> I have this matrix [20*4 - but it could be n*4 , with n~100,000] in
> file "EL_list" like this:
> 
>     1,      1,      2,      3
>      2,      4,      1,      5
>      3,      5,      1,      6
>      4,      7,      5,      6
>      5,      8,      7,      9
>      6,      8,      5,      7
>      7,     10,      9,      7
>      8,     10,     11,     12
>      9,      7,     13,     10
>     10,     14,     15,     16
>     11,     14,     17,     15
>     12,     17,     14,     18
>     13,     13,     16,     10
>     14,     16,     15,     11
>     15,     16,     11,     10
>     16,     19,     20,     21
>     17,     22,     15,     20
>     18,     17,     20,     15
>     19,     23,     20,     24
>     20,     25,     24,     20
> 
> I would like to replace some numbers in "EL_list" but only in columns
> 2,3,4 using the criterium by line in file "criterium" (column 1 are
> the new numbers, column 2 the old ones).
> 
> 1	1
> 2	3
> 3	5
> 4	12
> 5	13
> 6	14
> 7	15
> 8	16
> 9	17
> 10	18
> 11	19
> 12	10
> 13	21
> 14	22
> 15	23
> 16	24
> 17	25
> 
> For example all the 7 have to replaced by 15 and so on..
> 
> -- How to implement it in a fast end efficient code?
 >
Read the contents of "criterium" into a dict with the old value as the
key and the new value as the value and then iterate through the matrix
replacing the values in columns 2 to 4 with criterium.get(current_value,
current_value).

Incidentally, the singular of "criteria" is "criterion" because it's
Greek, not Latin.