Senior Python Developer

Senior Python Developer

Salary: From £50,000 per annum, depending on experience

Location: Remote, open to candidates anywhere in the UK. If you like to work alongside colleagues in person, our offices are in Birmingham, Bristol, Exeter and London.

Term/Hours: Permanent, 32-40 hours per week. We are flexible on working pattern, so please tell us what suits you in your application.

Closing date for applications: Monday 12th October 2026

We welcome applications from all suitably qualified candidates regardless of sex, gender identity, age, disability, ethnicity, religion or belief, sexual orientation, or any other protected characteristic.

We are only accepting direct applications (no recruiters please).

Unfortunately, we cannot consider applications requiring visa sponsorship now, or in the future.

About the Role

We are looking for a Senior Python Developer (or someone operating close to senior level) to join our five-person energy development team. You will help lead the design and implementation of Python packages building on the Home Energy Model that will enable the next generation of energy performance assessment.

You will work closely with DESNZ, external collaborators, our internal domain experts and your dev team, turning tangible and pressing user needs into reliable, maintainable Python software. The team is supportive and high-performing, and the work has a direct impact on carbon reduction.

This role includes line management. You may already manage one or more developers, or you may be ready to take that step, supported by our programme of leadership and management training. Either way, you will help the people you manage to do their best work and develop their careers.

What you will do

· Design, build and improve Python packages for modelling, simulation and data processing.

· Lead engineering decisions, architecture discussions and technical problem solving.

· Turn analytical and modelling needs into shippable software.

· Line manage one or more developers: regular one-to-ones, objective setting, performance reviews and support for their development.

· Mentor colleagues across the team and set a strong example through code reviews, pairing and knowledge sharing.

· Maintain high code quality through testing, documentation and thorough code reviews.

· Work across disciplines to integrate tools and deliver results for our customers.

· Drive continuous improvement in our tools, processes and engineering standards.

· Own your deliverables and keep projects moving with urgency and accountability.

About Us

City Science is an SME founded in 2015 with one core mission: delivering decarbonisation. We help organisations that are serious about net zero achieve meaningful, quantifiable carbon reductions quickly and efficiently.

We work collaboratively across the business to provide integrated solutions for a wide range of clients, from national bodies such as DESNZ and the Climate Change Committee (CCC) to forward-thinking local authorities such as Oxfordshire County Council. Our award-winning research, software and product development team builds innovative digital tools, such as our GIS software, Cadence, that sit at the heart of how we deliver our projects.

Requirements

Essential

· Strong professional experience as a Python developer, at or near senior level.

· Excellent command of Python and its ecosystem, including libraries, tooling and best practice.

· A track record of building production-grade applications, ideally in data-rich or scientific domains.

· The ability to write clean, maintainable, well-tested code.

· Experience line managing or formally mentoring developers, or a clear willingness and motivation to take on line management responsibilities.

· Strong problem-solving skills and the ability to explain technical ideas clearly to technical and non-technical audiences.

· Experience working in multidisciplinary teams.

Desirable

· Experience with Pydantic and/or JSON Schema.

· Familiarity with GitLab CI/CD.

· A strong grasp of geometry and physics, ideally including building physics.

· Understanding of decarbonisation and energy systems.

· Experience supporting the growth of more junior engineers, such as onboarding or coaching.

Aligned to Our Values

· Excellence: You hold high standards in your code, your solutions and your engineering decisions.

· Ownership & Accountability: You take responsibility for outcomes and proactively drive progress.

· Data Driven: You use evidence, analytical thinking and testing to guide your choices.

· Results Orientated: You focus on delivering outputs that create real-world impact.

· Adaptability & Learning: You embrace change, seek out new knowledge and learn quickly.

· Passion & Urgency: You care about what you build and work with purpose.

· Meritocracy: You value competence and fairness, and you help raise the bar for everyone around you.

· Entrepreneurial: You are resourceful and creative, and you bring ideas that move the business forward.

What We Offer

· Fully remote working, with optional access to our offices in Birmingham, Bristol, Exeter and London whenever you want them.

· Flexible working hours to support a healthy work-life balance.

· A talented, friendly and supportive team of engineers, data scientists and domain experts.

· Impactful projects in decarbonisation and sustainability.

· Real opportunities to grow, including as a people leader, and to shape exciting new products and capabilities.

· 25 days’ annual leave, plus bank holidays.

· Buy/sell annual leave policy.

· Membership of our group pension scheme.

· Enhanced maternity and paternity policy.

· Eye care policy.

· Cycle to work scheme.

· Employee assistance programme.

How to Apply

Please include:

· Your CV, highlighting relevant experience.

· Examples of projects that show your technical skills.

· Links to relevant code repositories or portfolio work.

· A short note on any line management or mentoring experience, or what draws you to taking on line management.

· Your preferred working hours and pattern.

We look forward to hearing from you.