python 如何写入现有txt文件中的特定行

Question

我正在编写一个脚本，该脚本读取输入文件，获取值并需要写入输出模板中的特定位置(行)，我绝对是菜鸟，做不到。它要么写入输出的第一行，要么写入最后一行。

opened file as 'r+'

used file.write(xyz) command

对于如何向 python 解释写入特定行感到困惑，例如。第 17 行(输出模板中的空行)

编辑:

with open (MCNP_input, 'r+') as M:
           line_to_replace = 17
           lines = M.readlines()
           if len(lines) > int (line_to_replace):
               lines[line_to_replace] = shape_sphere + radius + '\n'
               M.writelines(lines)

Answer 1

您可以读取该文件，然后写入某个特定行。

line_to_replace = 17 #the line we want to remplace
my_file = 'myfile.txt'

with open(my_file, 'r') as file:
    lines = file.readlines()
#now we have an array of lines. If we want to edit the line 17...

if len(lines) > int(line_to_replace):
    lines[line_to_replace] = 'The text you want here'

with open(my_file, 'w') as file:
    file.writelines( lines )