Add a line to a file if it not exist using python

Question

I have an xml file as follows:

Answer 1

Your question is based on lines in text files, but the input file is clearly XML, so assuming you actually want to add an Import if it doesn't exist, try this:

import xml.dom.minidom

importstring = "$(Projectname).targets"
filename = "test.xml"

tree = xml.dom.minidom.parse(filename)
Project = tree.getElementsByTagName("Project")[0]

for Import in Project.getElementsByTagName("Import"):
    if Import.getAttribute("Project") == importstring:
        break
else: # note this is else belongs to the for, not the if
    newImport = xml.dom.minidom.Element("Import")
    newImport.setAttribute("Project", importstring)
    Project.appendChild(newImport)

tree.writexml(open(filename, 'w'))

Answer 2

Take the XML parser of your choice, parse the file, manipulate the file using the related API, write it back.