Codegen enables traversing and manipulating collections through the List and Dict classes. These APIs work consistently across Python and TypeScript while preserving formatting and structure.

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Core Concepts

The List and Dict classes provide a consistent interface for working with ordered sequences of elements. Key features include:
  • Standard sequence operations (indexing, length, iteration)
  • Automatic formatting preservation
  • Safe modification operations
  • Language-agnostic behavior
  • Comment and whitespace preservation
Collections handle:
  • Proper indentation
  • Delimiters (commas, newlines)
  • Multi-line formatting
  • Leading/trailing whitespace
  • Nested structures

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List Operations

Lists in both Python and TypeScript can be manipulated using the same APIs: 
# Basic operations
items_list = file.get_symbol("items").value  # Get list value
first = items_list[0]        # Access elements
length = len(items_list)     # Get length
items_list[0] = "new"       # Modify element
items_list.append("d")      # Add to end
items_list.insert(1, "x")   # Insert at position
del items_list[1]           # Remove element

# Iteration
for item in items_list:
    print(item.source)

# Bulk operations
items_list.clear()          # Remove all elements

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Single vs Multi-line Lists

Collections automatically preserve formatting: 
# Source code:
items = [a, b, c]
config = [
    "debug",
    "verbose",
    "trace",
]

# Manipulation code:
items_list = file.get_symbol("items").value
items_list.append("d")    # Adds new element

config_list = file.get_symbol("config").value
config_list.append("info")  # Adds with formatting

# Result:
items = [a, b, c, d]
config = [
    "debug",
    "verbose",
    "trace",
    "info",
]

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Dictionary Operations

Dictionaries provide a similar consistent interface: 
# Basic operations
settings = file.get_symbol("settings").value  # Get dict value
value = settings["key"]     # Get value
settings["key"] = "value"   # Set value
del settings["key"]         # Remove key
has_key = "key" in settings # Check existence

# Iteration
for key in settings:
    print(f"{key}: {settings[key]}")

# Bulk operations
settings.clear()           # Remove all entries