astropy.io.fits.diff:ImageDataDiff.__init__

Parameters

a : BaseHDU

An HDU object.

b : BaseHDU

An HDU object to compare to the first HDU object.

numdiffs : int, optional

The number of pixel/table values to output when reporting HDU data differences. Though the count of differences is the same either way, this allows controlling the number of different values that are kept in memory or output. If a negative value is given, then numdiffs is treated as unlimited (default: 10).

rtol : float, optional

The relative difference to allow when comparing two float values either in header values, image arrays, or table columns (default: 0.0). Values which satisfy the expression

$$\left|a-b\right|>\text{atol}+\text{rtol}\cdot \left|b\right|$$

are considered to be different. The underlying function used for comparison is numpy.allclose.

atol : float, optional

The allowed absolute difference. See also rtol parameter.