Language Reference

Collections

Work with lists and dictionaries using clear, readable statements.

Next: strings Loops

Collection patterns

  • Initialize lists and dictionaries inline.
  • Use readable list comprehensions.
  • Access items with brackets.

Lists and dictionaries

Create collections in a single line, then access items with standard Python notation.

collections.pln 
create a list named users with ["Ada", "Lin", "Sam"]
create a dictionary named profile with {"name": "Ada", "role": "admin"}
print profile["role"]

Updating collections

Append to lists and update dictionary keys with readable assignments.

updates.pln 
create a list named users with ["Ada", "Lin"]
create a dictionary named profile with {"name": "Ada", "role": "engineer"}
set users to users + ["Sam"]
set profile["team"] to "platform"
print users[0]
print profile["team"]

Membership and size

Use in and len() to check membership and size.

membership.pln 
create a list named users with ["Ada", "Lin", "Sam"]
if "Ada" in users then print "User exists"
set total to len(users)
print "User count: " + str(total)

Nested collections

Store structured records as dictionaries inside lists.

nested.pln 
create a list named users with [
    {"name": "Ada", "active": true},
    {"name": "Lin", "active": false}
]
print users[0]["name"]

Readable list building

Use natural language filters to build new lists from existing data.

list_build.pln 
create a list of user["name"] for each user in users if user["active"] is true

Python collection helpers

Valid Python lines pass through, so list and dictionary methods are available when needed.

interop_collections.pln 
users = ["Ada", "Lin"]
users.append("Sam")
last_user = users.pop()
profile = {"name": "Ada"}
role = profile.get("role", "guest")
print last_user
print role

Organization tips

  • Prefer dictionaries for labeled data and lists for sequences.
  • Keep collection names plural to clarify intent.
  • Use list creation lines to keep transformations readable.