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Python for Quantitative Finance / Built-In Data Structures

Strings, Tuples, and Lists: Choosing the Right Sequence

This unit has now built four sequence types — str, tuple, range, and list — each introduced separately, for a specific purpose. This short note steps back and puts them side by side: what operations do all four share, what distinguishes them, and — most practically — how does a programmer decide which one to reach for in a given situation? The single deciding factor, as this note will argue, is almost always mutability, with a handful of secondary considerations (element homogeneity, dictionary-key eligibility) settling the remaining cases.
Learning objectives. By the end of this note you should be able to:
  • list the operations common to all four sequence types (str, tuple, range, list) and identify which types support concatenation and repetition and which do not;
  • state, and apply, the deciding rule for choosing between a tuple and a list in a given design situation;
  • use the key str methods (split, find, replace, count, lower, rstrip) for common text-processing tasks;
  • build a list incrementally with .append inside a for loop — the standard idiom for producing a filtered or transformed list from an existing sequence.

In this lesson

  1. The common sequence interface
  2. String-specific methods

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