npz

Documentation

Overview

Package npz provides read/write access to files with compressed NumPy data file format:

https://numpy.org/neps/nep-0001-npy-format.html

Index

• func Read(r io.ReaderAt, name string, ptr any) error
• func Write(name string, vs map[string]any) error
• type Reader
  • func NewReader(r io.ReaderAt, size int64) (*Reader, error)
  • func Open(name string) (*Reader, error)
  • func (r *Reader) Close() error
  • func (r *Reader) Header(name string) *npy.Header
  • func (r *Reader) Keys() []string
  • func (r *Reader) Open(name string) (io.ReadCloser, error)
  • func (r *Reader) Read(name string, ptr any) error
• type Writer
  • func Create(name string) (*Writer, error)
  • func NewWriter(w io.Writer) *Writer
  • func (w *Writer) Close() error
  • func (w *Writer) Write(name string, v any) error

Examples

• Create
• Open
• Read
• Reader
• Write
• Writer

Functions

func Read

func Read(r io.ReaderAt, name string, ptr any) error

Read reads the item named name from the reader r and stores the extracted data into ptr.

Example

package main

import (
	"fmt"
	"log"
	"os"

	"codeberg.org/sbinet/npyio/npz"
)

func main() {
	f, err := os.Open("../testdata/data_float64_corder.npz")
	if err != nil {
		log.Fatalf("could not open npz file: %+v", err)
	}
	defer f.Close()

	var f0 []float64
	err = npz.Read(f, "arr0.npy", &f0)
	if err != nil {
		log.Fatalf("could not read value from npz file: %+v", err)
	}

	var f1 []float64
	err = npz.Read(f, "arr1.npy", &f1)
	if err != nil {
		log.Fatalf("could not read value from npz file: %+v", err)
	}

	fmt.Printf("arr0: %v\n", f0)
	fmt.Printf("arr1: %v\n", f1)

}

Output:
arr0: [0 1 2 3 4 5]
arr1: [0 1 2 3 4 5]

func Write

func Write(name string, vs map[string]any) error

Write writes the values vs to the named npz archive file.

The data-array will always be written out in C-order (row-major).

Example

package main

import (
	"log"

	"codeberg.org/sbinet/npyio/npz"
)

func main() {
	err := npz.Write("out.npz", map[string]any{
		"arr0.npy": []float64{0, 1, 2, 3, 4, 5},
		"arr1.npy": []float32{0, 1, 2, 3, 4, 5},
	})
	if err != nil {
		log.Fatalf("could not save to npz file: %+v", err)
	}

}

Types

type Reader

type Reader struct {
	// contains filtered or unexported fields
}

Reader reads data from a compressed NumPy data file.

Example

package main

import (
	"fmt"
	"log"
	"os"

	"codeberg.org/sbinet/npyio/npz"
)

func main() {
	f, err := os.Open("../testdata/data_float64_corder.npz")
	if err != nil {
		log.Fatalf("could not open npz file: %+v", err)
	}
	defer f.Close()

	stat, err := f.Stat()
	if err != nil {
		log.Fatalf("could not stat npz file: %+v", err)
	}

	r, err := npz.NewReader(f, stat.Size())
	if err != nil {
		log.Fatalf("could not open npz archive: %+v", err)
	}

	for _, name := range r.Keys() {
		fmt.Printf("%s: %v\n", name, r.Header(name))
	}

	var f0 []float64
	err = r.Read("arr0.npy", &f0)
	if err != nil {
		log.Fatalf("could not read value from npz file: %+v", err)
	}

	var f1 []float64
	err = r.Read("arr1.npy", &f1)
	if err != nil {
		log.Fatalf("could not read value from npz file: %+v", err)
	}

	fmt.Printf("arr0: %v\n", f0)
	fmt.Printf("arr1: %v\n", f1)

}

Output:
arr1.npy: Header{Major:1, Minor:0, Descr:{Type:'<f8', Fortran:false, Shape:[6 1]}}
arr0.npy: Header{Major:1, Minor:0, Descr:{Type:'<f8', Fortran:false, Shape:[2 3]}}
arr0: [0 1 2 3 4 5]
arr1: [0 1 2 3 4 5]

func NewReader

func NewReader(r io.ReaderAt, size int64) (*Reader, error)

NewReader reads the compressed NumPy data from r, which is assumed to have the given size in bytes.

func Open

func Open(name string) (*Reader, error)

Open opens the named compressed NumPy data file for reading.

Example

package main

import (
	"fmt"
	"log"

	"codeberg.org/sbinet/npyio/npz"
)

func main() {
	f, err := npz.Open("../testdata/data_float64_corder.npz")
	if err != nil {
		log.Fatalf("could not open npz file: %+v", err)
	}
	defer f.Close()

	for _, name := range f.Keys() {
		fmt.Printf("%s: %v\n", name, f.Header(name))
	}

	var f0 []float64
	err = f.Read("arr0.npy", &f0)
	if err != nil {
		log.Fatalf("could not read value from npz file: %+v", err)
	}

	var f1 []float64
	err = f.Read("arr1.npy", &f1)
	if err != nil {
		log.Fatalf("could not read value from npz file: %+v", err)
	}

	fmt.Printf("arr0: %v\n", f0)
	fmt.Printf("arr1: %v\n", f1)

}

Output:
arr1.npy: Header{Major:1, Minor:0, Descr:{Type:'<f8', Fortran:false, Shape:[6 1]}}
arr0.npy: Header{Major:1, Minor:0, Descr:{Type:'<f8', Fortran:false, Shape:[2 3]}}
arr0: [0 1 2 3 4 5]
arr1: [0 1 2 3 4 5]

func (*Reader) Close

func (r *Reader) Close() error

Close closes the NumPy compressed data reader. Close doesn't close the underlying reader.

func (*Reader) Header

func (r *Reader) Header(name string) *npy.Header

Header returns the NumPy header metadata for the named array.

func (*Reader) Keys

func (r *Reader) Keys() []string

Keys returns the names of the NumPy data arrays.

func (*Reader) Open

func (r *Reader) Open(name string) (io.ReadCloser, error)

Open opens the named npy section in the npz archive.

func (*Reader) Read

func (r *Reader) Read(name string, ptr any) error

Read reads the named NumPy array data into the provided pointer.

Read returns an error if the on-disk data type and the provided one don't match.

type Writer

type Writer struct {
	// contains filtered or unexported fields
}

Writer writes data to a compressed NumPy data file.

Example

package main

import (
	"log"
	"os"

	"codeberg.org/sbinet/npyio/npz"
)

func main() {
	f, err := os.Create("out.npz")
	if err != nil {
		log.Fatalf("could not create npz file: %+v", err)
	}
	defer f.Close()

	wz := npz.NewWriter(f)
	defer wz.Close()

	err = wz.Write("arr0.npy", []float64{0, 1, 2, 3, 4, 5})
	if err != nil {
		log.Fatalf("could not write value arr0.npy to npz file: %+v", err)
	}

	err = wz.Write("arr1.npy", []float32{0, 1, 2, 3, 4, 5})
	if err != nil {
		log.Fatalf("could not write value arr1.npy to npz file: %+v", err)
	}

	err = wz.Close()
	if err != nil {
		log.Fatalf("could not close npz archive: %+v", err)
	}

	err = f.Close()
	if err != nil {
		log.Fatalf("could not close npz file: %+v", err)
	}

}

func Create

func Create(name string) (*Writer, error)

Create creates the named compressed NumPy data file for writing.

Example

package main

import (
	"log"

	"codeberg.org/sbinet/npyio/npz"
)

func main() {
	f, err := npz.Create("out.npz")
	if err != nil {
		log.Fatalf("could not create npz file: %+v", err)
	}
	defer f.Close()

	err = f.Write("arr0.npy", []float64{0, 1, 2, 3, 4, 5})
	if err != nil {
		log.Fatalf("could not write value arr0.npy to npz file: %+v", err)
	}

	err = f.Write("arr1.npy", []float32{0, 1, 2, 3, 4, 5})
	if err != nil {
		log.Fatalf("could not write value arr1.npy to npz file: %+v", err)
	}

	err = f.Close()
	if err != nil {
		log.Fatalf("could not close npz file: %+v", err)
	}

}

func NewWriter

func NewWriter(w io.Writer) *Writer

NewWriter returns a new npz writer.

The returned npz writer won't close the underlying writer.

func (*Writer) Close

func (w *Writer) Close() error

Close closes the npz archive. Close flushes the data to disk.

func (*Writer) Write

func (w *Writer) Write(name string, v any) error

Write writes the named NumPy array data to the npz archive.