如何使用python在文档中查找行号并在其下插入数据

Question

Hi I already have the search function sorted out:

def searchconfig():
    config1 = open("config.php", "r")
    b='//cats'
    for num, line in enumerate(config1,0):
        if b in line:
            connum = num + 1
            return connum
   config1.close()

This will return the line number of //cats, I then need to take the data underneath it put it in a tempoary document, append new data under the //cats and then append the data in the tempoary document to the original? how would i do this? i know that i would have to use 'a' instead of 'r' when opening the document but i do not know how to utilise the line number.

Answer 1

I think, the easiest way would be to read the whole file into a list of strings, work on that list and write it back afterwards.

# Read all lines of the file into a list of strings
with open("config.php", "r") as file:
  lines = list(file)
  file.close()

# This gets the line number for the first line containing '//cats'
# Note that it will throw an StopIteration exception, if no such line exists...
linenum = (num for (num, line) in enumerate(lines) if '//cats' in line).next()

# insert a line after the line containing '//cats'
lines.insert(linenum+1, 'This is a new line...')

# You could also replace the line following '//cats' like
lines[linenum+1] = 'New line content...'

# Write back the file  (in fact this creates a new file with new content)
# Note that you need to append the line delimiter '\n' to every line explicitely
with open("config.php", "w") as file:
  file.writelines(line + '\n' for line in lines)
  file.close()

Using "a" as mode for open would only let you append ath the end of the file.

You could use "r+" for a combined read/write mode, but then you could only overwrite some parts of the file, there is no simple way to insert new lines in the middle of the file using this mode.

Answer 2

You could do it like this. I am creating a new file in this example as it is usually safer.

with open('my_file.php') as my_php_file:
  add_new_content = ['%sNEWCONTENT' %line if '//cat' in line
                     else line.strip('\n')
                     for line in my_php_file.readlines()]
with open('my_new_file.php', 'w+') as my_new_php_file:
  for line in add_new_content:
    print>>my_new_php_file, line