Python - 在文件的特定行中的單詞後添加字符串

Question

我需要在文本文件的特定行中的單詞後添加字符串。原始文件是：

line 1: value1 
line 2: value2 
line 3: value3 
line 4: value4 
line 5: value5 

例如，我想在3號線加「NAME」剛過「行」，所以該文件將成爲：

line 1: value1 
line 2: value2 
line NAME 3: value3 
line 4: value4 
line 5: value5 

，你會怎麼做呢？

Answer 1

with open(file, 'r') as f: 
    lines = [] 
    for line in f: 
     split_lines = line.split(':') 
     if split_lines[0].endswith('3') is True: 
      lines.append(split_lines[0][:-1] + NAME + split_lines[1:]) 
     else: 
      lines.append(line) 

Answer 2

我會考慮這個問題：

line_number = 3#I understood you know this. right ? 
string_to_add = "NAME"#I understood you know this. right ? 
string_to_find = "line"#I understood you know this. right ? 
filename = "toto" 
with open(filename,"r") as f: 
    s = f.readlines() 
s[line_number] = s[line_number].replace(string_to_find,string_to_find+string_to_add) 
with open(filename,"w") as f: 
    for line in s: 
     f.write(line) 

這是真的，它似乎非常低效的（也可能不是一個大文件的現實）。我會好奇看到更好的方法。

Answer 3

這將查找以「第3行：」開始的行，並僅編輯此行，保留其餘行，並將文本寫入新文件。

with open('f1.txt', 'r') as f: 
    lines = [] 
    for line in f: 
     if line.startswith("line 3:"): 
      split_line = line.split() 
      split_line.insert(split_line.index("3:"), "NAME") 
      lines.append(' '.join(split_line) + '\n') 
     else: 
      lines.append(line) 

with open('f2.txt', 'w') as f: 
    for line in lines: 
     f.write(line) 

當您運行下面的代碼，

with open('f2.txt', 'r') as f: 
    for line in f: 
     print(line, end='') 

它打印：

line 1: value1 
line 2: value2 
line NAME 3: value3 
line 4: value4 
line 5: value5