Jane Street showing love to Python over OCAML as it expands its AI team

One of the most contentious factors about taking a job at Jane Street is its insistence on using OCAML over C++. Though many find it enjoyable to use, there are complaints that it can limit career opportunities outside the firm. Now, however, as Jane Street leans heavily into AI and machine learning, a much more transferable language is coming to the fore.

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In software engineer job listings at Jane Street, the firm says Python has "become a vital part of Jane Street’s research and trading work, acting as the go-to language for data analysis, visualization, and machine learning." Python experience is now a preference for a number of roles including data engineers, StatArb research analysts and, of course, its machine learning staff. 

Python isn't replacing OCAML at Jane Street, though. Jane Street's software engineer internships say applicants will be working with the incumbent language, but that some teams "also use Python," the implication being that no teams are purely Python yet. Jane Street says its Python ecosystem is still "relatively young," and is hiring a developer to build Python tools, most of which will be made in OCAML.

Jane Street's love for Python stems from its ease of use. In the firm's most recent 'Signals & Threads' podcast, it revealed that PyTorch was the most frequently used tool when creating machine learning models among its traders because it allowed them to "iterate really fast through their ideas." It has been using Python in a machine learning context for years, according to a 2020 edition of the podcast, but CTO Ron Minsky said the firm's Python systems previously lacked the "rich testing infrastructure" of its OCAML ones. Ex-researcher Laurent Mazare said this was less of an issue at the time because the Python Jane Street shipped was "fairly limited," but as its employees use the language more, the need for that infrastructure grows.

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