比较两个 CSV 文件并在同一个文件中写入差异作为 python 中的额外列

Question

Hey intelligent community,

I need a little bit of help because i think i don't see the the wood in the trees.

i have to CSV files that look like this:

Name,Number
AAC;2.2.3
AAF;2.4.4
ZCX;3.5.2


Name,Number
AAC;2.2.3
AAF;2.4.4
ZCX;3.5.5

I would like to compare both files and than write any changes like this:

Name,Number,Changes
AAC;2.2.3
AAF;2.4.4
ZCX;5.5.5;change: 3.5.2

So on every line when there is a difference in the number, i want to add this as a new column at the end of the line.
The Files are formated the same but sometimes have a new row so thats why i think i have to map the keys.

I come this far but now iam lost in my thoughts:

Python 3.10.9

 import csv Reading the first csv and set mapping with open('test1.csv', 'r') as csvfile: reader= csv.reader(csvfile) rows = list(reader) file1_dict = {row[1]: row[0] for row in rows} Reading the second csv and set mapping with open('test2.csv', 'r') as csvfile: reader= csv.reader(csvfile) rows = list(reader) file2_dict = {row[1]: row[0] for row in rows} comparing the keys and find the diff for k in test1_dict: if test1_dict[k]:= test2:dict[k] test1_dict[k] = test2_dict[k] for row in rows: if row[1] == k. row:append(test2_dict[k]) #write the csv (not sure how to add the word "change.") with open('test1,csv', 'w': newline ='') as csvfile. writer = csv.writer(csvfile) writer.writerows(rows)

If i try this, i don't get a new column, it just "updates" the csv file with the same columns.

For example this code gives me the diff row but i'am not able to just add it to existing file and row.

with open('test1.csv') as fin1:
  with open('test2.csv') as fin2:
    read1 = csv.reader(fin1)
    read2 = csv.reader(fin2)
    diff_rows = (row1 for row1, row2 in zip(read1, read2) if row1 != row2)
    with open('test3.csv', 'w') as fout:
      writer = csv.writer(fout)
      writer.writerows(diff_rows)

Does someone have any tips or help for my problem? I read many answers on here but can't figure it out.

Thanks alot.

@bigkeefer Thanks for your answer, i tried to change it for the delimiter; but it gives an "list index out of range error".

with open('test3.csv', 'r') as file1:
    reader = csv.reader(file1, delimiter=';')
    rows = list(reader)[1:]
    file1_dict = {row[0]: row[1] for row in rows}
with open('test4.csv', 'r') as file2:
    reader = csv.reader(file2, delimiter=';')
    rows = list(reader)[1:]
    file2_dict = {row[0]: row[1] for row in rows}
new_file = ["Name;Number;Changes\n"]
with open('output.csv', 'w') as nf:
    for key, value in file1_dict.items():
        if value != file2_dict[key]:
            new_file.append(f"{key};{file2_dict[key]};change: {value}\n")
        else:
            new_file.append(f"{key};{value}\n")
    nf.writelines(new_file)

Answer 1

You will need to adapt this to overwrite your first file etcetera, as you mentioned above, but I've left it like this for your testing purposes. Hopefully this will help you in some way.

I've assumed you've actually got the headers above in each file. If not, remove the slicing on the list creations, and change the new_file variable assignment to an empty list ([]).

with open('f1.csv', 'r') as file1:
    reader = csv.reader(file1, delimiter=";")
    rows = list(reader)[1:]
    file1_dict = {row[0]: row[1] for row in rows if row}
with open('f2.csv', 'r') as file2:
    reader = csv.reader(file2, delimiter=";")
    rows = list(reader)[1:]
    file2_dict = {row[0]: row[1] for row in rows if row}
new_file = ["Name,Number,Changes\n"]
for key, value in file1_dict.items():
    if value != file2_dict[key]:
        new_file.append(f"{key};{file2_dict[key]};change: {value}\n")
    else:
        new_file.append(f"{key};{value}\n")
with open('new.csv', 'w') as nf:
    nf.writelines(new_file)