pipdeptree_library_api_dependency_graph_filter_by_package.py

11. # Note: pipdeptree is primarily a command-line tool. 
22. # The official way to use it as a library involves importing its internal API:
33. 
44. from pipdeptree._models import PackageDAG
55. from pipdeptree._discovery import get_installed_distributions
66. 
77. # 1. Get all installed distributions in the current environment
88. pkgs = get_installed_distributions()
99. 
1010. # 2. Build the Dependency Graph
1111. tree = PackageDAG.from_pkgs(pkgs)
1212. 
1313. # 3. Example: Filter the tree to show dependencies of a specific package (e.g., 'flask')
1414. # This mimics the CLI command: pipdeptree -p flask
1515. flask_tree = tree.filter_nodes(include={'flask'}, exclude=None)
1616. 
1717. # 4. Print the resulting tree structure
1818. for parent, children in flask_tree.items():
1919.     print(f"{parent.project_name} ({parent.version})")
2020.     for child in children:
2121.         print(f"  - {child.project_name} (requires {child.specifier})")