Generate a schema from a YAML file (or from stdin.)

schema.py

#!/usr/bin/env python3
'''
schema.py - Generate a schema from a YAML file (or from stdin.)

Required:
    pip install PyYAML

Usage:
    python3 schema.py < PATH
    python3 schema.py PATH [PATH ...]
'''

import sys

from yaml import load
try:
    from yaml import CLoader as Loader
except ImportError:
    from yaml import Loader

###############################################################################

def schema_sorter(data):
    def compare(key):
        '''Simple types first, then dict types, then list types.'''
        if isinstance(data[key], dict):
            return 'zz_dict_'+key
        if isinstance(data[key], list):
            return 'zz_list_'+key
        else:
            return 'aa_'+key
    return compare

def get_schema(data, indent='  ', prefix=''):
    type_name = type(data).__name__
    result = [f'<{type_name}>']
    if isinstance(data, dict):
        ordered_keys = sorted(data.keys(), key=schema_sorter(data))
        for key in ordered_keys:
            child_schema = get_schema(data[key], indent, prefix+indent)
            result.append(f'{prefix}{key}: {child_schema}')
    elif isinstance(data, list):
        child_schema = get_schema(data[0], indent, prefix+indent)
        result.append(f'{prefix}-{indent[1:]}{child_schema}')
    return '\n'.join(result)


def load_schema(file, indent='  '):
    data = load(file, Loader=Loader)
    return get_schema(data, indent)


def main(args):
    if not args:
        print(load_schema(sys.stdin))
    for path in args:
        print(f'# {path}')
        with open(path) as f:
            print(load_schema(f))
    return sys.exit(0)


if __name__ == '__main__':
    sys.exit(main(sys.argv[1:]))