Python小程序 - 替换文件内容

    1. 写入文件c:\a.txt
        1）共写入10行
        2）每行内容 0123456789

# 1
ls = '0123456789'
ln = 10
with open("c:/a.txt", 'w+',encoding='UTF-8') as f:
    for i in range(ln):
        f.write(ls+'\n')

########################################

# 2
ln = 10
with open("c:/a.txt", 'w+',encoding='UTF-8') as f:
    for i in range(ln):
        ls = str(i)
        for j in range(ln):
            ls = ls + str(j)
        f.write(ls+'\n')

##
00123456789
10123456789
20123456789
30123456789
40123456789
50123456789
60123456789
70123456789
80123456789
90123456789

    2. 替换文件内容
       1）全文替换指定内容

# replace '1' with 'a'

# 1
with open("c:/a.txt", 'r',encoding='UTF-8') as f:
    fl = f.readlines()

    for fs in fl:
        print(fs.replace('1','a'))
        
###############################################

# 2-1
with open("c:/a.txt", 'r',encoding='UTF-8') as f:
    fl = f.readline()

    while fl:
        print(fl.replace('1','a'))
        fl = f.readline()

# 2-2
fl = ''
with open("c:/a.txt", 'r',encoding='UTF-8') as f:
    fl = f.readlines()

    for fn in range(len(fl)):
        print(fl[fn].replace('1','a'))
        fl[fn] = fl[fn].replace('1','a')
        print(fl[fn])

with open("c:/a.txt", 'w',encoding='UTF-8') as f:
    f.writelines(fl)

####
00a23456789
a0a23456789
20a23456789
30a23456789
40a23456789
50a23456789
60a23456789
70a23456789
80a23456789
90a23456789

      2）替换指定行的内容

# replace line 5
# replace '1' with 'A'
rl = 5
rw = 'A'
with open("c:/a.txt", 'r',encoding='UTF-8') as f:
    fl = f.readlines()

    fl[rl-1] = fl[rl-1].replace('1',rw)

with open("c:/a.txt", 'w',encoding='UTF-8') as f:
    f.writelines(fl) 

##
00123456789
10123456789
20123456789
30123456789
40A23456789
50123456789
60123456789
70123456789
80123456789
90123456789

    3. 定义函数 
 

def replace_word_in_file(file_path,old_word,new_word,line_num):
    fl = '' # file content
    
    with open(file_path, 'r',encoding='UTF-8') as f:
        fl = f.readlines()

        if(line_num>len(fl) or line_num<0 ):
            print('Wrong line number, pleae check.')
        # replace all in file              
        elif(line_num == 0):
            for fn in range(len(fl)):
                fl[fn] = fl[fn].replace(old_word,new_word)
        else:
            fl[line_num-1] = fl[line_num-1].replace(old_word,new_word)

    with open(file_path, 'w',encoding='UTF-8') as f:
        f.writelines(fl)


if __name__ == "__main__":
    replace_word_in_file("c:/a.txt",'1','A',0)  # 1  
    replace_word_in_file("c:/a.txt",'1','A',5)  # 2
    replace_word_in_file("c:/a.txt",'1','A',11) # 3
    replace_word_in_file("c:/a.txt",'1','A',-1) # 4

## 1
00A23456789
A0A23456789
20A23456789
30A23456789
40A23456789
50A23456789
60A23456789
70A23456789
80A23456789
90A23456789

## 2
00123456789
10123456789
20123456789
30123456789
40A23456789
50123456789
60123456789
70123456789
80123456789
90123456789

## 3
Wrong line number, pleae check.

## 4
Wrong line number, pleae check.

-- 创作助手提问

1. python readline 逐行读出

   with open('file.txt', 'r') as file:
       line = file.readline()
       while line:
           print(line)
           line = file.readline()

2. python 写入文件

   # 打开文件，以写入模式（'w'）进行操作
   file = open('example.txt', 'w')
   
   # 写入文本
   file.write('Hello, world!')
   
   # 关闭文件
   file.close()