Search and match data from two files in Python - python-2.7

Question

I have two different files; A reference file and a data sets with different length.
A reference file ("location.dat") contains:
40505 5.0666667 102.2166667
40517 5.6833333 101.8500000
40586 5.7666667 102.2000000
40587 5.8166667 102.0500000
40663 6.0333333 102.1166667
41525 5.5500000 100.4833333
41529 5.3500000 100.4000000
...............
...............
A data sets ("input.dat") contains:
40517 2014 12 18 0 17.4
40586 2014 12 18 0 9.9
40587 2014 12 18 0 15.5
40663 2014 12 18 0 30.9
41525 2014 12 18 0 0
41529 2014 12 18 0 0
41540 2014 12 18 0 0
41543 2014 12 18 0 0
41548 2014 12 18 0 0
41549 2014 12 18 0 0
41551 2014 12 18 0 0
41610 2014 12 18 0 0
Question:
How to search and match data set so that the output file will combine certain selected values from both files like this:
output.dat
40517 5.6833333 101.8500000 17.4
40586 5.7666667 102.2000000 9.9
40587 5.8166667 102.0500000 15.5
............
...........
The current script is:
data1=np.loadtxt('location.dat')
lats1=data1[:,1]
lons1=data1[:,2]
code1=data1[:,0]
data2=np.loadtxt('input.dat')
rain=data2[:,5]
code2=data2[:,0]
ind=[]
for i in range(len(data1)):
dist=code1[i]
ind.append(np.where(dist==np.int(dist))[0][0])
rain2=rain[ind]
data3=np.array([code1,lats1,lons1,rain2])
data3=np.transpose(data3)
np.savetxt('output.dat',data3,fmt='%9.3f')
The current result
40517.000 5.683 101.850 0.000
40586.000 5.767 102.200 0.000
40587.000 5.817 102.050 0.000
40663.000 6.033 102.117 0.000
41525.000 5.550 100.483 0.000
41529.000 5.350 100.400 0.000
41540.000 5.383 100.550 0.000
The rain2 values did not properly append from the input file. How to convert the first column output to be integer?.Any ideas of what went wrong??.TQ

Answer 1

The line
ind.append(np.where(dist==np.int(dist))[0][0])
does not make sense in your code. This will always append 0 if distis an integer (as dist==np.int(dist) is simply the array [True])
A better way to solve your problem is to create a look-up table from the data in location.dat
data1=np.loadtxt('location.dat')
lookup = {int(round(id_)):(lat,long) for id_, lat, long in data1}
Please note that the best way to convert a float to an int in python is to use int(round(i))
You can then iterate over the data in your other file and create the proper line
data3 = []
for line in data2:
ind = int(round(line[0]))
data3.append([ind, lookup[ind][0], lookup[ind][1], line[5]])
To save the data, you may want to format and write the line one after the other or use savetxt.