I think that the numpy route that @Bera suggested is better, but you can do what you want also with a text editor and gdal_translate.
First, find out how many rows and columns you have in the data and have a look at how ESRI AsciiGrid files are written https://github.com/OSGeo/gdal/blob/master/autotest/gdrivers/data/aaigrid/nodata_float.asc
Add header lines at the beginning of the text file with these values:
ncols what-you-have-in-data
nrows what-you-have-in-data
xllcorner 0
yllcorner 0
cellsize 1
Change the commas between the cell values into spaces. The linefeeds can stay as they are. These both small test files seem to work in the same way.
asciitest1.asc
==============
ncols 5
nrows 2
xllcorner 0
yllcorner 0
cellsize 1
1 2 3 4,5
6 7 8 9 10
asciitest2.asc
==============
ncols 5
nrows 2
xllcorner 0
yllcorner 0
cellsize 1
1 2 3 4 5 6 7 8 9 10
Test with gdalinfo:
gdalinfo asciitest.asc
Driver: AAIGrid/Arc/Info ASCII Grid
Files: asciitest.asc
Size is 5, 2
Origin = (0.000000000000000,2.000000000000000)
Pixel Size = (1.000000000000000,-1.000000000000000)
Corner Coordinates:
Upper Left ( 0.0000000, 2.0000000)
Lower Left ( 0.0000000, 0.0000000)
Upper Right ( 5.0000000, 2.0000000)
Lower Right ( 5.0000000, 0.0000000)
Center ( 2.5000000, 1.0000000)
Band 1 Block=5x1 Type=Float32, ColorInterp=Undefined
Convert into TIFF:
gdal_translate asciitest2.asc asciitest2.tif
Input file size is 5, 2
0...10...20...30...40...50...60...70...80...90...100 - done.
