This is an announcement of the first official release ver.1.0 of a Python system NZMATH for number theory. We overview all functions in NZMATH 1.0, show main properties after former report on NZMATH 0.5.0, and describe new features for stable development. The most important point of the release is that we can now treat number fields. The second big change is that new type of polynomial programs are provided. Elliptic curve primality proving and its related programs are also available, where we partly use a library outside NZMATH as an advantage of writing the system only by Python. On method of development, a new feature is that NZMATH is registered on SourceForge as an open source project to keep continuous development of the project. This is a unique attempt among existing systems for number theory.