Write file to a directory that doesn't exist

You need to first create the directory.

The mkdir -p implementation from this answer will do just what you want. mkdir -p will create any parent directories as required, and silently do nothing if it already exists.

Here I've implemented a safe_open_w() method which calls mkdir_p on the directory part of the path, before opening the file for writing:

import os, os.path
import errno

# Taken from https://stackoverflow.com/a/600612/119527
def mkdir_p(path):
    try:
        os.makedirs(path)
    except OSError as exc: # Python >2.5
        if exc.errno == errno.EEXIST and os.path.isdir(path):
            pass
        else: raise

def safe_open_w(path):
    ''' Open "path" for writing, creating any parent directories as needed.
    '''
    mkdir_p(os.path.dirname(path))
    return open(path, 'w')

with safe_open_w('/Users/bill/output/output-text.txt') as f:
    f.write(...)

Make liberal use of the os module:

import os

if not os.path.isdir('/Users/bill/output'):
    os.mkdir('/Users/bill/output')

with open('/Users/bill/output/output-text.txt', 'w') as file_to_write:
    file_to_write.write("{}\n".format(result))

For Python 3 can use with pathlib.Path:

from pathlib import Path

p = Path('Users') / 'bill' / 'output'
p.mkdir(exist_ok=True)
(p / 'output-text.txt').open('w').write(...)