Map[K]V

Map[K]V

PyGo provides first-class support for generic map types using the Map[K, V] syntax. Maps are type-safe at compile time and mechanically transpiled to idiomatic Go map[K]V and Python dict[K, V] types.

Basic Usage

model Config:
  app_name: String
  settings: Map[String, String]      # Map of string keys to string values
  thresholds: Map[String, Int]      # Map of string keys to int values

Model Values

model User:
  name: String

model Team:
  name: String
  members: Map[String, User]  # Map of user IDs to User objects

Nested Maps

model MultiTenantConfig:
  data: Map[String, Map[String, String]]  # 2D map of strings

Type Safety

Maps are validated at compile time:

config = Config(
    app_name="MyApp",
    settings={"theme": "dark", "lang": "en"},
    thresholds={"max_retries": 3, "timeout": 30}
)

# Valid — accessing a known key type
theme = config.settings["theme"]

# Invalid — the transpiler rejects this at compile time
# config.settings[123]  # Error: 123 is not String

Generated Code

Go:

type Config struct {
    AppName    string
    Settings   map[string]string
    Thresholds map[string]int
}

Python:

from typing import Dict

class Config(BaseModel):
    app_name: str
    settings: Dict[str, str]
    thresholds: Dict[str, int]

Database Representation

Maps are stored in the database as follows:

• SQLite: JSON-encoded as TEXT
• PostgreSQL: JSONB column type

CREATE TABLE config (
    id INTEGER PRIMARY KEY,
    app_name TEXT NOT NULL,
    settings TEXT,     -- JSON: {"theme": "dark", "lang": "en"}
    thresholds TEXT    -- JSON: {"max_retries": 3, "timeout": 30}
);

Map Operations

PyGo supports the following operations on maps:

Insert/Update

config.settings["theme"] = "light"

Get with Default

theme = config.settings.get("theme", "dark")

Delete

del config.settings["theme"]

Contains Check

if "theme" in config.settings:
    print(config.settings["theme"])

Keys / Values / Items

keys = config.settings.keys()      # ["theme", "lang"]
values = config.settings.values()  # ["light", "en"]
items = config.settings.items()    # [("theme", "light"), ("lang", "en")]

Nullable Maps

Use Map[K, V]? for nullable maps:

model Config:
  app_name: String
  settings: Map[String, String]? = None  # Can be NULL

Best Practices

• Use Map[String, String] for flexible key-value configuration
• Use Map[String, Model] for lookup tables and indexed collections
• Use Map[String, Map[String, V]] sparingly — consider flattening the structure
• Always provide default empty maps to avoid null issues