Python：如何将值从另一个csv文件写入一个csv文件

Question

For index.csv file, its fourth column has ten numbers ranging from 1 - 5 . Each number can be regarded as an index, and each index corresponds with an array of numbers in filename.csv .

The row number of filename.csv represents the index, and each row has three numbers. My question is about using a nesting loop to transfer the numbers in filename.csv to index.csv .

from numpy import genfromtxt
import numpy as np
import csv
import collections

data1 = genfromtxt('filename.csv', delimiter=',')
data2 = genfromtxt('index.csv', delimiter=',')

out = np.zeros((len(data2),len(data1)))

for row in data2:

    for ch_row in range(len(data1)):

        if (row[3] == ch_row + 1):

            out = row.tolist() + data1[ch_row].tolist()

            print(out)

            writer = csv.writer(open('dn.csv','w'), delimiter=',',quoting=csv.QUOTE_ALL)

            writer.writerow(out)

For example, the fourth column of index.csv contains 1,2,5,3,4,1,4,5,2,3 and filename.csv contains:

# filename.csv

20 30 50 
70 60 45 
35 26 77 
93 37 68 
13 08 55 

What I need is to write the indexed row from filename.csv to index.csv and store these number in 5th, 6th and 7th column:

# index.csv

#   4 5  6  7 
... 1 20 30 50 
... 2 70 60 45 
... 5 13 08 55 
... 3 35 26 77 
... 4 93 37 68 
... 1 20 30 50 
... 4 93 37 68 
... 5 13 08 55 
... 2 70 60 45 
... 3 35 26 77

If I do "print(out)", it comes out a correct answer. However, when I input "out" in the shell, there are only one row appears like [1.0, 1.0, 1.0, 1.0, 20.0, 30.0, 50.0]

What I need is to store all the values in the "out" variables and write them to the dn.csv file.

Answer 1

with open('dn.csv','w') as f:
    writer =  csv.writer(f, delimiter=',',quoting=csv.QUOTE_ALL)
        for row in data2:
            idx = row[3]
            out = [idx] + [x for x in data1[idx-1]]
            writer.writerow(out)

Answer 2

This ought to do the trick for you:

Code:

from csv import reader, writer


data = list(reader(open("filename.csv", "r"), delimiter=" "))

out = writer(open("output.csv", "w"), delimiter=" ")

for row in reader(open("index.csv", "r"), delimiter=" "):
    out.writerow(row + data[int(row[3])])

index.csv:

0 0 0 1
0 0 0 2
0 0 0 3

filename.csv:

20 30 50
70 60 45
35 26 77
93 37 68
13 08 55

This produces the output:

0 0 0 1 70 60 45
0 0 0 2 35 26 77
0 0 0 3 93 37 68

Note : There's no need to use numpy here. The stadard library csv module will do most of the work for you.

I also had to modify your sample datasets a bit as what you showed had indexes out of bounds of the sample data in filename.csv .

Please also note that Python ( like most languages ) uses 0th indexes. So you may have to fiddle with the above code to exactly fit your needs.