callable_sample.py

#!/usr/bin/env python
"""Use of a callable to implement lazy evaluation of keys in a dict."""

data = {
    'name': 'John',
    'surname': 'Smith',
    'full_name': lambda x: '{name} {surname}'.format(**x)
}


if __name__ == '__main__':
    print(data)
    for k, v in data.items():
        if callable(v):
            data[k] = v(data)
    print(data)