# [Numpy-discussion] Reading and Comparing Two Files

Friedrich Romstedt friedrichromstedt@gmail....
Sun Feb 28 06:24:36 CST 2010

```2010/2/28 Robert Love <rblove_lists@comcast.net>:
> What is the efficient numpy way to compare data from two different files?  For the nth line in each file I want to operate on the numbers.   I've been using loadtxt()
>
> data_5x5 = N.loadtxt("file5")
>
> data_8x8 = N.loadtxt("file8")
>
> for line in data_5x5:
>        pos5 = N.array([line[0], line[1],  line[2]])

I believe there are several ways of doing that, and mine might not be
the most efficient at all:

for line5, line8 in zip(data_5x5, data_8x8):
# line5 and line8 are row vectors of paired lines
pass

complete = numpy.hstack(data_5x5, data_8x8)  # If data_5x5.shape[0] ==
data_8x8.shape[0], i.e., same number of rows.
for line in complete:
# complete is comprised of concatenated row vectors.
pass

for idx in xrange(0, min(data_5x5.shape[0], data_8x8.shape[0])):
line5 = data_5x5[idx]
line8 = data_8x8[idx]
# Do sth with the vectors. Or:
a1 = data_5x5[idx, (0, 1, 2)]  # Extract items 0, 1, 2 of line idx
of first file.
a2 = data_8x8[idx, (0, 42)]   # Extract items 0, 42 of line idx of
second file.

...

Friedrich
```

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