Snake case

Snake case (or snake_case) is the practice of writing compound words or phrases in which the elements are separated with one underscore character (_) and no spaces, with each element's initial letter usually lowercased within the compound and the first letter either upper or lower case—as in "foo_bar" and "Hello_world". It is commonly used in computer code for variable names, and function names, and sometimes computer filenames. At least one study found that readers can recognize snake case values more quickly than camel case.

The use of underscores as word separators in identifiers in programming languages is old, dating to the late 1960s. It is particularly associated with C, being found in The C Programming Language (1978), and contrasted with Pascal case, an older term for camel case. However, the convention traditionally had no specific name: the Python style guide refers to it simply as "lower_case_with_underscores".

The name "snake_case" comes from the Ruby community, where it was coined in 2004 by Gavin Kistner, writing:

"BTW...what *do* you call that naming style? snake_case? That's what I'll call it until someone corrects me."

As of 2015^[update] names for other delimiter-separated naming conventions for multiple-word identifiers have not been standardized, although some terms have increasing levels of usage, such as lisp-case, kebab-case, SCREAMING_SNAKE_CASE, etc.

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