我正在制作一个程序,在计算机上搜索.fts和.fits文件,打开文件,检索与标题中特定关键字对应的信息,并将文件重命名为该关键字。
我遇到了一个问题,我一直收到KeyError,因为在文件中找不到我正在搜索的标头关键字。有办法绕过这个吗?我希望能够搜索各种关键字并做一些事情,即使该关键字在文件中不存在。
这是代码:
from astropy.io import fits
import os
for i in os.listdir(os.getcwd()):
if i.endswith(".fits") or i.endswith(".fts"):
hdulist = fits.open(i)
DATEOBS_header = hdulist[0].header['DATE-OBS']
EXPTIME_header = int(round(hdulist[0].header['EXPTIME']))
CCDTEMP_header = int(round(hdulist[0].header['CCD-TEMP']))
XBINNING_header = hdulist[0].header['XBINNING']
FILTER_header = hdulist[0].header['FILTER']
IMAGETYP_header = hdulist[0].header['IMAGETYP']
OBJECT_header = hdulist[0].header['OBJECT']
DATEandTIME = DATEOBS_header[0:]
YEAR = DATEandTIME[0:4]
MONTH = DATEandTIME[5:7]
DAY = DATEandTIME[8:10]
#TIME = DATEOBS_header[11:]
HOUR = DATEandTIME[11:13]
MINUTE = DATEandTIME[14:16]
SECONDS = DATEandTIME[17:]
DATE = str(YEAR) + str(MONTH) + str(DAY) + 'at' + str(HOUR) + str(MINUTE) + str(SECONDS)
if IMAGETYP_header == 'Light Frame':
newname = str(OBJECT_header) + '_' + str(DATE) + '_' + str(CCDTEMP_header) + 'temp_' + str(XBINNING_header) + 'bin_' + str(EXPTIME_header) + 'exptime_' + str(FILTER_header) + '.fits'
if IMAGETYP_header == 'Dark Frame':
newname = 'Dark_' + str(DATE) + 'at' + str(TIME) + '_' + str(CCDTEMP_header) + 'temp_' + str(XBINNING_header) + 'bin_' + str(EXPTIME_header) + 'exptime' + '.fits'
if IMAGETYP_header == 'Flat Field':
newname = 'Flat_' + str(DATE) + 'at' + str(TIME) + '_' + str(CCDTEMP_header) + 'temp_' + str(XBINNING_header) + 'bin_' + str(EXPTIME_header) + 'exptime_' + str(FILTER_header) + '.fits'
prevname = i
os.rename(prevname, newname)
hdulist.close()
continue
else:
continue
这就是我得到的错误:
Traceback (most recent call last):
File "glo1.py", line 9, in <module>
DATEOBS_header = hdulist[0].header['DATE-OBS']
File "/home/luisgeesb/.local/lib/python2.7/site-packages/astropy/io/fits/header.py", line 151, in __getitem__
card = self._cards[self._cardindex(key)]
File "/home/luisgeesb/.local/lib/python2.7/site-packages/astropy/io/fits/header.py", line 1723, in _cardindex
raise KeyError("Keyword %r not found." % keyword)
KeyError: "Keyword 'DATE-OBS' not found."
为了防止这些类型的异常停止您的程序,您可以捕获它们,如下所示:
try:
DATEOBS_header = hdulist[0].header['DATE-OBS']
except KeyError:
DATEOBS_header = None
或者,使用字典的.get()
方法,该方法检查键是否存在以及是否不返回默认值,而不是引发异常。返回的默认值为None
。
如果您这样做,您还需要设置一些合理的默认值,或者捕捉那些正在强制转换值的情况(因为您不能强制转换None
)。
最后,无论何时从文件中读取数据,都应该始终假设数据格式错误/垃圾,并进行一些防御性编程。在您的代码中,您假设为CCDTEMP
返回的值是一个数字,但如果文件已损坏或为空呢?您的应用程序无法处理此情况。
以下是一些试图捕捉尽可能多错误的代码:
DATEOBS_header = hdulist[0].header.get('DATE-OBS')
XBINNING_header = hdulist[0].header.get('XBINNING')
FILTER_header = hdulist[0].header.get('FILTER')
IMAGETYP_header = hdulist[0].header.get('IMAGETYP')
OBJECT_header = hdulist[0].header.get('OBJECT')
# For these two, you need to either set a default
# Here I am setting the default to 0, ------------v
EXPTIME_header = int(round(hdulist[0].header.get('EXPTIME', 0)))
# Or you need to check for a value :
ccdtemp_value = hdulist[0].header.get('CCD-TEMP')
try:
ccdtemp_value = int(round(ccdtemp_value))
except ValueError:
# This means, the value was either None (header does not exist)
# or it was something that can't be converted to a number
# since it cannot be converted to a number, we do not know
# if the value is None or something like an empty string,
# so we explicitly set the value to None
ccdtemp_value = None
CCDTEMP_header = ccdtemp_value
假设hdulist[0].header
给您一个dict
实例,您可以执行类似的操作
DATEOBS_header = hdulist[0].header.get('DATE-OBS')
如果密钥'DATE-OBS'
不存在,则返回None
。
请参阅https://docs.python.org/2/library/stdtypes.html#dict.get了解更多详细信息。