Choosing the Right Structure

Most beginners ask: “Which one should I use?”

Here is the simple decision system.

Use list when

• order matters
• you need duplicates
• you need indexing

Use tuple when

• order matters
• you want data to be fixed (no changes)

Use set when

• uniqueness matters
• you need fast membership tests

Use dict when

• you need key -> value lookup

Examples

Task: store user order list

Use list:

queue = ["Tom", "Sarah", "Mike"]

Task: store unique user emails

Use set:

emails = {"a@x.com", "b@x.com"}

Task: store user profile by id

Use dict:

users = {101: {"name":"Tom"}, 102: {"name":"Sarah"}}

Graph: quick decision

flowchart TD
  A[Need a container] --> B{Need key->value?}
  B -->|Yes| C[dict]
  B -->|No| D{Need uniqueness?}
  D -->|Yes| E[set]
  D -->|No| F{Need fixed/unchangeable?}
  F -->|Yes| G[tuple]
  F -->|No| H[list]

Remember

• Choose based on operations, not personal preference
• Correct structure makes code simpler and faster