Print plantuml instructions for an ER diagram of all Django models

django_model_er_plantuml_plot.py

from django.apps import apps

HEADER = """@startuml
skinparam linetype ortho
"""
FOOTER = """@enduml"""


Models = apps.get_models()

def format_model(M):
    return f'"{M._meta.app_label}.{M.__name__}"'

print(HEADER)
for Model in Models:
    model_ref = format_model(Model)
    print("entity %s {}" % model_ref)
for Model in Models:
    model_ref = format_model(Model)
    for field in Model._meta.fields:
        if field.is_relation:
            RelatedModel = field.related_model
            related_model_ref = format_model(RelatedModel)
            if field.one_to_one:
                if field.null:
                    rel_string = "|o--o|"
                else:
                    rel_string = "||--o|"
            # elif field.one_to_many:
            #     pass
            elif field.many_to_one:
                if field.null:
                    rel_string = "}o--o|"
                else:
                    rel_string = "}|--o|"
            elif field.many_to_many:

                rel_string = "}o--o{"
            else:
                print("ERROR")
                continue
            print(f"{model_ref} {rel_string} {related_model_ref}")
print(FOOTER)