csv file data appending using python-CodePudding

I've been trying to append certain data from input.csv to output.csv using python.

My code is as under:


    import csv
    from csv import writer
    from csv import reader
    
    
    csvPath = r'C:\Users\Nitin Kumar\Downloads\annual-enterprise-survey-2020-csv-new.csv'
    csvWrite = r'C:\Users\Nitin Kumar\Downloads\copied.csv'
    
    rslt=[]
    with open(csvPath, encoding='utf-8-sig') as csvfile:
    reader = csv.reader(csvfile)

    count=0
    fsa=[]
    for row in reader:
        count=count 1
        print(row)
        rslt.append(row)
        # if count>20:
        #     break
print(rslt)

with open(csvPath, 'r') as read_obj, \
        open(csvWrite, 'a', newline='') as write_obj:
    csv_reader = csv.reader(read_obj)
    csv_writer = csv.writer(write_obj)
    for row_ in csv_reader:
        row_.append(rslt)
        csv_writer.writerow(row_)

The input csv file is:


    Year,Industry_agg,Industry_code,Industry_name,Units,Variable_code,Variable_name,Variable_category,Value,Industry_code_ANZSIC06
    2020,Level 1,99999,All industries,Dollars (millions),H01,Total income,Financial performance,"7,33,258",ANZSIC06 divisions A-S 
    2020,Level 1,99999,All industries,Dollars (millions),H04,Sales,Financial performance,"6,60,630",ANZSIC06 divisions A-S
    2020,Level 1,99999,All industries,Dollars (millions),H05,"Interest, dividend",Financial performance,"54,342",ANZSIC06 divisions A-S 
    2020,Level 1,99999,All industries,Dollars (millions),H07,Non-operating income,Financial performance,"18,285",ANZSIC06 divisions A-S
    2020,Level 1,99999,All industries,Dollars (millions),H08,Total expenditure,Financial performance,"6,54,872",ANZSIC06 divisions A-S

The output file I'm getting is:

    Name
    Nitin
    Nitin1
    Nitin2
    Nitin3
    Nitin4
    Nitin5
    Year,Industry_agg,Industry_code,Industry_name,Units,Variable_code,Variable_name,Variable_category,Value,Industry_code_ANZSIC06,[]
    2020,Level 1,99999,All industries,Dollars (millions),H01,Total income,Financial performance,"7,33,258",ANZSIC06 divisions A-S ,[]
    2020,Level 1,99999,All industries,Dollars (millions),H04,Sales,Financial performance,"6,60,630",ANZSIC06 divisions A-S,[]
    2020,Level 1,99999,All industries,Dollars (millions),H05,"Interest, dividend",Financial performance,"54,342",ANZSIC06 divisions A-S ,[]
    2020,Level 1,99999,All industries,Dollars (millions),H07,Non-operating income,Financial performance,"18,285",ANZSIC06 divisions A-S,[]
    2020,Level 1,99999,All industries,Dollars (millions),H08,Total expenditure,Financial performance,"6,54,872",ANZSIC06 divisions A-S ,[]

However, the output csv file was having following data previously before appending data:


    Name
    Nitin
    Nitin1
    Nitin2
    Nitin3
    Nitin4
    Nitin5

I need the output file to be like below:


    Name,Year,Industry_agg,Industry_code,Industry_name,Units,Variable_code,Variable_name,Variable_category,Value,Industry_code_ANZSIC06
    Nitin,2020,Level 1,99999,All industries,Dollars (millions),H01,Total income,Financial performance,"7,33,258",ANZSIC06 divisions A-S 
    Nitin1,2020,Level 1,99999,All industries,Dollars (millions),H04,Sales,Financial performance,"6,60,630",ANZSIC06 divisions A-S
    Nitin2,2020,Level 1,99999,All industries,Dollars (millions),H05,"Interest, dividend",Financial performance,"54,342",ANZSIC06 divisions A-S 
    Nitin3,2020,Level 1,99999,All industries,Dollars (millions),H07,Non-operating income,Financial performance,"18,285",ANZSIC06 divisions A-S
    Nitin4,2020,Level 1,99999,All industries,Dollars (millions),H08,Total expenditure,Financial performance,"6,54,872",ANZSIC06 divisions A-S
    Nitin5

I need my output file to append the input data but not able to get the desired result. Previously I was even able to add header in outout csv file. Gone through lot of codes already present but none of them helped me in this.

CodePudding user response：

Combine the lines of the input and output files, and overwrite the output file with the new lines.

# read input file
with open(input_filename, 'r') as input_file:
    input_lines = input_file.read().split('\n')
    input_lines.append('') # because your input file has 
                           # one less line than your output file
    
# read output file
with open(output_filename, 'r') as output_file:
    output_lines = output_file.read().split()

# combine lines of input and output files
new_lines = [output_line   ','   input_line for 
             input_line, output_line in zip(input_lines, output_lines)]

# overwrite output file with new lines
with open(output_filename, 'w') as output_file:
    for i, line in enumerate(new_lines):
        end = '\n' if i   1 < len(new_lines) else '' # make new line except 
                                                     # after last line
        output_file.write(line   end)

CodePudding user response：

You might find it better to use Python's zip_longest() function which is able to easily deal with lists of different lengths.

Try the following:

import csv
from itertools import zip_longest

csvPath = r'C:\Users\Nitin Kumar\Downloads\annual-enterprise-survey-2020-csv-new.csv'
csvWrite = r'C:\Users\Nitin Kumar\Downloads\copied.csv'

# Read all the existing entries
existing = []       # Rows holding: Name, Nitin, Nitin1

with open(csvWrite, encoding='utf-8-sig') as f_existing:
    existing = list(csv.reader(f_existing))

# Read the new entries and combine with the existing entries
with open(csvPath, 'r') as f_input, \
    open(csvWrite, 'w', newline='') as f_output:
    
    csv_input = csv.reader(f_input)
    csv_output = csv.writer(f_output)
    
    for row_existing, row_new in zip_longest(existing, csv_input, fillvalue=''):
        csv_output.writerow([*row_existing, *row_new])

The last line takes all elements from an existing row and combines them with all elements from the new row to create a combined output list row.