Python—在文件的特定行中的单词后添加字符串

我需要在文本文件的特定行中的单词后添加字符串。原始文件是：

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

例如，我想在第3行“line”之后添加“NAME”，这样文件将变成：

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

<>你会怎么做？

< P>我会考虑这个：

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)

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)

的确，它看起来效率很低（对于大文件来说可能不现实）。我很想看到更好的方法。

< P>我会考虑这一点：

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)

---

的确，它看起来效率很低（对于大文件来说可能不现实）。我很想找到更好的方法。

这会查找以“第3行：”开头的行，只编辑这一行，保留其余行，并将文本写入新文件

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)

当您运行下面的代码时

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

---

这将查找以“line 3:”开头的行，并仅编辑这一行，保留其余行，然后将文本写入新文件

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)

当您运行下面的代码时

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

---

你在哪里重写文件？@Stéphane只需在写入模式下打开同一个文件，并在列表行中写入行。你在哪里重写文件？@Stéphane只需在写入模式下打开同一个文件，并在列表行中写入行。你能发布你的代码吗？你能发布你的代码吗？