当键在字典中时出现键错误

Question

只是试图从一堆照片的 EXIF 数据中提取一些纬度/经度信息，但代码会抛出 a ，KeyError即使稍后（成功）使用该键来打印特定坐标。

有问题的字典是“ tags” -'GPS GPSLatitude'并且'GPS GPSLongitude'都是tags.keys(); 我已经三重检查了。

那么对于为什么会抛出关键错误有什么直觉tags['GPS GPSLatitude']吗tags['GPS GPSLongitude']？

import os
import exifread

output = dict()
output['name'] = []
output['lon'] = []
output['lat'] = []

for file in os.listdir(path):
    if file.endswith(".JPG"):
        full_path = path + file
        print (file) #check to ensure all files were found
        output['name'].append(file) #append photo name to dictionary
        f = open(full_path, 'rb') #open photo
        tags = exifread.process_file(f) #read exifdata
#       lon = tags['GPS GPSLongitude'] #this + next line = one method
#       output['lon'].append(lon)
#       output['lat'].append(tags['GPS GPSLatitude']) # = cleaner second method
        for tag in tags.keys():
            if tag in ('GPS GPSLongitude','GPS GPSLatitude'):
                print ("Key: %s, value %s" % (tag, tags[tag])) #successfully prints lat/lon coords with 'GPS GPSLongitude' and 'GPS GPSLatitude' as keys

更新：

print (tags.keys())这是- 您将在其中看到GPS GPSLatitude和的输出。GPS GPSLongitude另外，手动检查了我正在使用的子集中的所有照片是否有 GPS 数据。

dict_keys(['GPS GPSImgDirection', 'EXIF SceneType', 'MakerNote Tag 0x0006', 'GPS GPSDestBearing', 'Thumbnail XResolution', 'EXIF BrightnessValue', 'GPS GPSAltitude', 'GPS GPSLongitude', 'EXIF LensSpecification', 'GPS GPSAltitudeRef', 'GPS GPSSpeedRef', 'GPS GPSDestBearingRef', 'EXIF WhiteBalance', 'Thumbnail ResolutionUnit', 'EXIF FocalLengthIn35mmFilm', 'EXIF SceneCaptureType', 'Image Model', 'MakerNote Tag 0x0008', 'Image Make', 'EXIF ShutterSpeedValue', 'MakerNote Tag 0x0007', 'EXIF ExifImageWidth', 'EXIF LensModel', 'Image YResolution', 'EXIF ComponentsConfiguration', 'Image GPSInfo', 'EXIF ISOSpeedRatings', 'EXIF ExposureMode', 'EXIF Flash', 'EXIF FlashPixVersion', 'GPS GPSLatitudeRef', 'EXIF ExposureBiasValue', 'Thumbnail JPEGInterchangeFormatLength', 'Thumbnail Compression', 'Image YCbCrPositioning', 'EXIF MakerNote', 'EXIF FNumber', 'JPEGThumbnail', 'MakerNote Tag 0x0001', 'EXIF ColorSpace', 'EXIF SubSecTimeDigitized', 'Thumbnail JPEGInterchangeFormat', 'MakerNote Tag 0x0004', 'EXIF SubjectArea', 'Image ResolutionUnit', 'EXIF SensingMethod', 'Image DateTime', 'Image Orientation', 'EXIF ExifVersion', 'Image ExifOffset', 'GPS GPSImgDirectionRef', 'MakerNote Tag 0x0014', 'Thumbnail YResolution', 'EXIF DateTimeOriginal', 'MakerNote Tag 0x0005', 'EXIF LensMake', 'EXIF DateTimeDigitized', 'MakerNote Tag 0x0003', 'GPS GPSTimeStamp', 'EXIF ExposureTime', 'GPS Tag 0x001F', 'EXIF SubSecTimeOriginal', 'GPS GPSLatitude', 'Image Software', 'EXIF ApertureValue', 'GPS GPSDate', 'EXIF ExposureProgram', 'GPS GPSSpeed', 'EXIF ExifImageLength', 'EXIF MeteringMode', 'GPS GPSLongitudeRef', 'EXIF FocalLength', 'Image XResolution'])

追溯

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-14-949ba89a1248> in <module>()
     16 #        lon = tags["GPS GPSLongitude"]
     17 #        output['lon'].append(lon)
---> 18         output['lat'].append(tags['GPS GPSLatitude'])
     19         for tag in tags.keys():
     20             if tag in ('GPS GPSLongitude','GPS GPSLatitude'):

KeyError: 'GPS GPSLatitude'

照片链接：https://drive.google.com/a/cornell.edu/file/d/0B1DwcbbAH1yuTEs0cUhhODdlNnc/view

这张照片的打印声明的输出

IMG_6680.JPG
Key: GPS GPSLongitude, value [76, 29, 353/20]
Key: GPS GPSLatitude, value [42, 26, 5069/100]

Answer 1

GPS GPSLatitude并且GPS GPSLongitude可能不会出现在所有标签字典中。

您也可以使用tags['GPS GPSLatitude']&访问键，而不是使用&访问键。这将返回而不是抛出错误，您还可以应用 if-else 条件来验证这些键不存在的位置。tags['GPS GPSLongitude']tags.get('GPS GPSLatitude')tags.get('GPS GPSLongitude')None