writing to file very slow

[Skip Montanaro]

    Moritz> Everything seems to work fine, except for the fact that writing
    Moritz> the file is very slow (example: 4 minutes for 4 thousand
    Moritz> lines).

    ...

    Moritz>   varnames=""
    Moritz>   for z in range(len(results.listfields())-1):
    Moritz>     varnames += str(results.fieldname(z))+'|'
    Moritz>   varnames += str(results.fieldname(len(results.listfields())-1))
    Moritz>   f.write(varnames)
    Moritz>   f.write("\n")
    Moritz>   for x in range(results.ntuples()):
    Moritz>    var = ""
    Moritz>    for y in range(len(results.listfields())-1):
    Moritz>      var+=str(results.getresult()[x][y])+'|'
    Moritz>    var+=str(results.getresult()[x][len(results.listfields())-1])
    Moritz>    f.write(var)
    Moritz>    f.write('\n')

First thing I'd try is getting rid of the string extension using +=.  Also,
note that you have two nested for loops which makes your writing
proportional to the length of ntuples * the length of results.listfields().

For example:

    varnames = []
    for z in range(len(results.listfields())-1):
        varnames.extend([str(results.fieldname(z)),'|'])
    varnames.append(str(results.fieldname(len(results.listfields())-1)))
    f.write("".join(varnames))

I'm sure the logic can be further cleaned up, but my head is foggy this
morning with a cold.  Others with a clearer head will be able to help there.

Skip