Saving numpy array to txt file row wise

import numpy
a = numpy.array([1,2,3])

with open(r'test.txt', 'w') as f:
    f.write(" ".join(map(str, a)))

An alternative answer is to reshape the array so that it has dimensions (1, N) like so:

savetext(filename, a.reshape(1, a.shape[0]))

If numpy >= 1.5, you can do:

# note that the filename is enclosed with double quotes,
# example "filename.txt"

numpy.savetxt("filename", a, newline=" ")

Edit

several 1D arrays with same length

a = numpy.array([1,2,3])
b = numpy.array([4,5,6])
numpy.savetxt(filename, (a,b), fmt="%d")

# gives:
# 1 2 3
# 4 5 6

several 1D arrays with variable length

a = numpy.array([1,2,3])
b = numpy.array([4,5])

with open(filename,"w") as f:
    f.write("\n".join(" ".join(map(str, x)) for x in (a,b)))

# gives:
# 1 2 3
# 4 5

I found that the first solution in the accepted answer to be problematic for cases where the newline character is still required. The easiest solution to the problem was doing this:

numpy.savetxt(filename, [a], delimiter='\t')