Strings

Go / 13 Sep 2026 / 4 min read

Transform Unicode Text with strings.Map in Go

strings.Map applies one function to every rune in a UTF-8 string and builds a string from the returned runes. A mapping function can preserve a rune, replace it, or remove it entirely. That makes the API a compact fit for transformations whose rule is naturally expressed one Unicode code point at a time. mapped := strings.Map(func(r rune) rune { if r == '_' { return '-' } return r }, input) The operation is rune-oriented rather than byte-oriented. ASCII input still follows the same contract, but multibyte UTF-8 sequences arrive at the callback as decoded rune values.

Golang Strings

Go / 13 Sep 2026 / 4 min read

Split Text with Custom Rune Boundaries Using strings.FieldsFunc in Go

strings.FieldsFunc treats selected Unicode code points as boundaries and returns the non-empty text between them. That behavior fits inputs where separators belong to a class rather than one fixed substring: commas and semicolons, several punctuation marks, or any rune accepted by a deterministic predicate. fields := strings.FieldsFunc(input, func(r rune) bool { return r == ',' || r == ';' }) For alpha,,beta;gamma;, the result is []string{"alpha", "beta", "gamma"}. Consecutive matching runes form a boundary region, and matching runes at either edge do not produce empty elements.

Golang Strings

Go / 13 Sep 2026 / 4 min read

Split Once with strings.Cut in Go

strings.Cut separates a string around the first occurrence of a delimiter and reports whether that delimiter was present. That three-result contract matters in parsers where a missing separator is different from a separator followed by an empty value. before, after, found := strings.Cut(input, "=") When the separator exists, before contains the text preceding its first occurrence and after contains the remainder. When it does not exist, the function returns the original string, an empty second string, and false.

Golang Strings

Go / 13 Sep 2026 / 5 min read

Replace Non-Overlapping Substrings with strings.ReplaceAll in Go

strings.ReplaceAll replaces every non-overlapping occurrence of one literal string with another. There is no regular-expression syntax, callback, or token model involved: matching is based on the exact byte sequence supplied as old. result := strings.ReplaceAll("api/v1/users", "/v1/", "/v2/") The result is api/v2/users. This small contract makes the function suitable for fixed substitutions where every match receives the same replacement.

Golang Strings

Go / 13 Sep 2026 / 3 min read

Remove Prefixes with strings.CutPrefix in Go

Prefix removal often carries two pieces of information: the remaining text and whether the expected prefix was present. strings.CutPrefix represents both results in one operation instead of separating a prefix test from the removal that follows it. That distinction matters when an unchanged string is a valid result. strings.TrimPrefix returns the input unchanged when the prefix is absent, so its return value alone cannot report presence. strings.CutPrefix returns the remainder plus a boolean that preserves that fact explicitly.

Golang Strings

Go / 13 Sep 2026 / 4 min read

Remove Explicit Suffixes with strings.CutSuffix in Go

strings.CutSuffix removes one exact trailing string and reports whether that suffix was present. The boolean result is the key distinction from operations that only return transformed text: callers can keep suffix recognition separate from the remaining content. base, found := strings.CutSuffix(name, ".json") If name ends in .json, base contains the preceding text and found is true. Otherwise, base is the original string and found is false. The operation does not scan for a matching fragment in the middle and does not repeatedly strip the suffix.

Golang Strings

Python / 08 Sep 2026 / 12 min read

Process Template Strings Safely with Python T-Strings

Python’s f-strings are excellent when the desired result is immediately a string. That same immediacy becomes a limitation when an application needs to inspect interpolated values before deciding how they should be represented. Python 3.14 adds template string literals, usually called t-strings, for that boundary. A t-string looks much like an f-string, but it does not immediately collapse its literal text and interpolated values into one str. Instead, it produces a structured Template object from string.templatelib.

Python Security

Rust / 01 Sep 2026 / 5 min read

Choosing &str, String, and Cow for Rust Text APIs

Rust has several common ways to represent UTF-8 text, and choosing between &str, String, and Cow<'a, str> is fundamentally an ownership decision. The best API is usually the one that asks callers for the least ownership it needs and returns ownership only when the result requires it. Use &str when you only need to read text A string slice borrows UTF-8 text owned elsewhere: fn is_blank(value: &str) -> bool { value.trim().is_empty() } This accepts borrowed views into a String, string literals, and other string slices without taking ownership or allocating.

Rust Strings