Copylines = []
lines.append('def print_success():')
lines.append('    print "sucesss"')
"\n".join(lines)

If you're building something complex dynamically:

Copyclass CodeBlock():
    def __init__(self, head, block):
        self.head = head
        self.block = block
    def __str__(self, indent=""):
        result = indent + self.head + ":\n"
        indent += "    "
        for block in self.block:
            if isinstance(block, CodeBlock):
                result += block.__str__(indent)
            else:
                result += indent + block + "\n"
        return result

You could add some extra methods, to add new lines to the block and all that stuff, but I think you get the idea..

Example:

Copyifblock = CodeBlock('if x>0', ['print x', 'print "Finished."'])
block = CodeBlock('def print_success(x)', [ifblock, 'print "Def finished"'])
print block

Output:

Copydef print_success(x):
    if x>0:
        print x
        print "Finished."
    print "Def finished."

You should use the print() function which is available since Python 2.6+

from __future__ import print_function  # Only needed for Python 2
print("hi there", file=f)

For Python 3 you don't need the import, since the print() function is the default.

The alternative in Python 3 would be to use:

with open('myfile', 'w') as f:
    f.write('hi there\n')  # python will convert \n to os.linesep

Quoting from Python documentation regarding newlines:

When writing output to the stream, if newline is None, any '\n' characters written are translated to the system default line separator, os.linesep. If newline is '' or '\n', no translation takes place. If newline is any of the other legal values, any '\n' characters written are translated to the given string.

See also: Reading and Writing Files - The Python Tutorial

You need to change the second flag when opening the file:

• w for only writing (an existing file with the same name will be erased)
• a opens the file for appending

Your code then should be:

with open("output.txt", "a") as f: