sentinels_library_unique_missing_value_placeholder_pattern.py

1from sentinels import Sentinel
2
3# Create a sentinel object
4NOTHING = Sentinel('NOTHING')
5
6def get_value(data, key, default=NOTHING):
7    value = data.get(key, default)
8    if value is NOTHING:
9        return "Value not found"
10    return f"Found: {value}"
11
12# Example usage
13data_store = {"a": 1, "b": None}
14
15print(get_value(data_store, "a"))      # Output: Found: 1
16print(get_value(data_store, "b"))      # Output: Found: None (distinguishes None from missing)
17print(get_value(data_store, "c"))      # Output: Value not found