Development of NZMATH. NZMATH is a system oriented to calculations of number theory, based on Python. Currently, it has several basic data types and several modules for number theoretic computations. NZMATH has two key visions 1) user / developer fusion and 2) speed of development, and the system has been growing along the lines. The development is of open source by nature, and we are making effort to be as agile as possible. There are many areas to be developed, especially a module for algebraic numbers is awaited. Some experimental user interface construction is also discussed.