Merge all csv in folder by columns without pandas

Maxim Oleynik 0
Viewed 43

I'm using python3 and I want to merge few csv files by columns. Is it possible to do without pandas?

For example if I have this two csv

df1:
Name   Surname PCName
Max    Petrov  wrs123
Ivan   Ivanov  wrs321

df2:
Surname  Name   PCName
Sidorov  Vasily wrs223
Dmitriev Alex   wrs331

With pandas I've got this solution:

import os
import pandas as pd # $ pip install pandas
import time

def cls():
    os.system('cls' if os.name=='nt' else 'clear')
cls()

today = time.strftime("%y%m%d")
fldpath = 'C:/tmp2/test/'
filepath = fldpath+today+"_merged.csv"

print(os.listdir(fldpath))
print("type begining of file names")
fmask = input()
file_list = [fldpath + f for f in os.listdir(fldpath) if f.startswith(fmask)]
csv_list = []
for file in sorted(file_list):
    csv_list.append(pd.read_csv(file).assign(File_Name = os.path.basename(file)))

csv_merged = pd.concat(csv_list, ignore_index=True)
csv_merged.to_csv(filepath, index=False)
csv python
1 Answers

You could use a Python DictReader() and DictWriter() to do this as follows:

import csv
import os
import time

def cls():
    os.system('cls' if os.name=='nt' else 'clear')
cls()

today = time.strftime("%y%m%d")
fldpath = 'C:/tmp2/test/'
filepath = fldpath + today + "_merged.csv"

print(os.listdir(fldpath))
print("type beginning of file names")
fmask = input()
file_list = [fldpath + f for f in os.listdir(fldpath) if f.startswith(fmask)]

with open(filepath, 'w', newline='') as f_output:
    csv_output = csv.DictWriter(f_output, fieldnames=["Name", "Surname", "PCName"])
    csv_output.writeheader()
    
    for file in sorted(file_list):
        with open(file) as f_input:
            csv_input = csv.DictReader(f_input)
            csv_output.writerows(csv_input)

For your given example, this would produce an output of:

Name,Surname,PCName
Max,Petrov,wrs123
Ivan,Ivanov,wrs321
Vasily,Sidorov,wrs223
Alex,Dmitriev,wrs331

This assumes each CSV file has the same field names (order is not important)

Martin Evans0
Related