Python-将多个文件数据写入主文件
文件处理是任何Web应用程序的重要组成部分。
Python具有创建，读取，更新和删除文件的几种功能。
要写入现有文件，必须向open()函数添加参数-
“a”-追加-将追加到文件末尾
“w”-写-将覆盖任何现有内容
示例
import os
# list the files in directory
lis = os.listdir('D:\\python' '\\data_files\\data_files')
print(lis)
tgt = os.listdir('D:\\python' '\\data_files\\target_file')
file_dir ='D:\\python\\data_files\\data_files'
out_file = r'D:\\python\\data_files\\target_file\\master.txt'
ct = 0
print('target file :', tgt)
try:
# check for if file exists
# if yes delete the file
# otherwise data will be appended to existing file
if len(tgt)>0:
os.remove('D:\\python' '\\data_files\\target_file\\master.txt')
open(tgt, 'a').close()
else:
# create an empty file
open(tgt, 'a').close()
except:
head = open('D:\\python' '\\data_files\\target_file\\master.txt', 'a+')
line ='empno, ename, sal'
# write header to output
print(head, line)
head.close()
# below loop to write data to output file
for line1 in lis:
f_dir = file_dir+'\\'+line1
# open files in read mode
in_file = open(f_dir, 'r+')
# open output in append mode
w = open(out_file, 'a+')
d = in_file.readline()
d = in_file.readlines()
w.write("\n")
for line2 in d:
print(line2)
w.write(line2)
ct = ct + 1
w.close()
#using pandas
import pandas as pd
# pd.read_csv creates dataframes
df1 = pd.read_csv('D:\python\data_files\data_files\emp_1.txt')
df2 = pd.read_csv('D:\python\data_files\data_files\emp_2.txt')
df3 = pd.read_csv('D:\python\data_files\data_files\emp_3.txt')
frames = [df1, df2, df3]
# concat function concatenates the frames
result = pd.concat(frames)
# to_csv function writes output to file
result.to_csv('D:\\python\\data_files' '\\target_file\\master.txt', encoding ='utf-8', index = False)