Question

Possible Duplicate:
Add a line to a file if it not exist using python

I have a text file as follows:

  <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003" DefaultTargets="Build" ToolsVersion="4.0">
  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
  <ImportGroup Label="ExtensionTargets">
  </ImportGroup>
</Project>

I want to add a line <Import Project="$(ProjectName).targets" /> between
</ImportGroup> and </Project> as follows

  <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003" DefaultTargets="Build" ToolsVersion="4.0">
  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
  <ImportGroup Label="ExtensionTargets">
  </ImportGroup>
  <Import Project="$(ProjectName).targets" />
</Project>

I used fileinput module to insert the line but i don’t want to add
<Import Project="$(ProjectName).targets" /> if it already exists in file
How can I do that?

Answer 1

You should read the whole file, or enough lines and check if the substring is in the content with:

'<Import Project="$(ProjectName).targets" />' in file_content

Or you could use a regex to make the search more robust:

import re
regex = re.compile(r'<Import Project="\$\(ProjectName\)\.targets\s*/>')
if not regex.search(file_content):
    insert_line_into_file()
else:
    #the line already exists