astropyiofits

astropyiofits is a Python library for reading and writing FITS files, a standard data format widely used in astronomy. It provides a high-level interface for manipulating FITS data within the NumPy-based ecosystem of Astropy, enabling users to access image and table data, headers, and metadata stored in FITS containers.

Historically, FITS I/O functionality began with PyFITS and was distributed as a separate package. It was later integrated into the Astropy project as astropy.io.fits, and the standalone distribution named astropyiofits is deprecated. New code should use astropy.io.fits within Astropy.

Its core concept is the header/data unit (HDU). The library loads FITS files into an HDUList consisting of a PrimaryHDU and any number of extension HDUs (ImageHDU, BinTableHDU, TableHDU, etc.). It provides functions and classes to read data (getdata, getval), access and modify headers, and write data back to disk (writeto). It supports binary and ASCII tables, memory-mapped arrays for large files, and basic data type handling via NumPy. It also offers compatibility with the PyFITS API to ease migration and scripting.

Usage is straightforward: open a file with fits.open, inspect structure with info, access data and headers via the HDU objects, and write changes with writeto. The module emphasizes portability across platforms and is a standard tool in the astronomy Python ecosystem.