backup a file in python

backup.py

def backup_file(file_path, backup_path=None, verbose=True):
    """
    If the given 'file_path' exists, this function creates a copy of it.
    Backup is done at 'backup_path'.backup# (backup_path defaults to
    'file_path'.
    If 'verbose' is set (defaults to True), prints output when backing up.
    """
    if not os.path.isfile(file_path):
        return
    if not backup_path:
        backup_path = file_path
    ensure_directory(backup_path)

    count = 1
    file_name_template = "{}.backup{}"
    backup_name = file_name_template.format(backup_path, count)
    while os.path.isfile(backup_name):
        count += 1
        backup_name = file_name_template.format(backup_path, count)

    with open(file_path) as original_file, \
            open(backup_name, "w") as backup_file:
        backup_file.write(original_file.read())

    if verbose:
        print(("'{}' already found! Backing the file up to '{}' before doing "
               "any changes.").format(file_path, backup_name))


def ensure_directory(file_path):
    d = os.path.dirname(file_path)
    if d and not os.path.exists(d):
        os.makedirs(d)