Astropy.io.fits

>>> hdulist = fits.open('input.fits')
>>> hdulist.info()

header

• each element of an HDUList is an HDU object with .header and .data attributes, which can be used to access the header and data portions of the HDU.

>>> hdulist[0].header['targname']

• To see the entire header as it appears in the FITS file (with the END card and padding stripped), simply enter the header object by itself, or print(repr(header)):
• It’s also possible to view a slice of the header:

>>> header[:2]

• Another way to either update an existing card or append a new one is to use the Header.set() method:

>>> prihdr.set('observer', 'Edwin Hubble')

fits table 的读与写

• 读

hdu = fits.open('SFH_LMC3_out.fits')
hdu.info() #看看哪些hdu
data=hdu[1].data
cols=hdu[1].columns
data.columns #看看有那些列
data.field(0) #读取第一列，也可以拿到列的名字，然后data['tag']读取
data[0] #第一行

• 修改columns中某个keyword的值

columns = fits.ColDefs(hdul[1].columns)
clumns1.change_attrib(col_name='DATA',attrib='format',new_value='8388608B')

• 写

from astropy.table import Table
t=Table([Bage,fzbin,Age_weight2],names=('Age','z','weights'))
t.write('SFH_LMC3_out.fits',format='fits')

• 更新

可以使用**HDUList.flush()方法将自open()**以来所做的所有更改写回原始文件。**close()**方法将对以更新模式打开的FITS文件执行相同的操作:

with fits.open('original.fits', mode='update') as hdul:
   # Change something in hdul.
   hdul.flush()

fits文件打开过多错误

• [1]
• fits.close()
• 可能还根系统设置有关

ulimit -a
ulimit -n 100000
vim /etc/security/limits.conf

• 把python的软限制编程硬限制,参见 [2],下面方法貌似也不管用

import resource
soft, hard = resource.getrlimit(resource.RLIMIT_NOFILE)
resource.setrlimit(resource.RLIMIT_NOFILE, (hard, hard))

• lsof -p 进程id > openfiles.log命令，获得当前占用句柄的全部详情进行分析
• 实测这两个效果不好（python 3.8）

• del hdu.data
• hdu = fits.open(fits_name,memmap=False) #打开fits文件数目比较多的情况下

fits image读写

n = np.arange(100.0) 
hdu = fits.PrimaryHDU(n)
hdu.writeto('new2.fits')
hdu.writeto('new2.fits')

• 如果超过一个hdu

>>> hdul = fits.HDUList([hdu])
>>> hdul.writeto('new1.fits')