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Question

我正在Mac OS上的python3中运行一个子进程，以从保存在本地目录中的许多图像中检索EXIF图像数据。

该代码间歇性地工作。子进程几乎每隔第3次调用都会返回字节对象（如预期的那样），只有它为空b''。

该故障并非特定于任何特定的图像文件（更改）。

我尝试了两个版本的代码，一个版本在其中调用Popen.wait（..）（示例在下面查找纬度），另一个版本在其中立即调用.communicate（）（在下面查找经度）。

print('.......========.......')
try:
    cmdLat = "mdls \"" + imagePath + "\" | grep Latitude | awk '{print $3}'"
    subprocess = Popen(cmdLat, shell=True, stdout=PIPE)
    Popen.wait(subprocess)
    lat = subprocess.communicate()[0]
    latFloat = float(lat.decode())
except Exception as e:
    print("Failed finding latitude, exception:", e)
    print("lat value: ", lat)

try:
    cmdLon = "mdls \"" + imagePath + "\" | grep Longitude | awk '{print $3}'"
    lon = (Popen(cmdLon, shell=True, stdout=PIPE).communicate()[0])
    lonFloat = float(lon.decode())
except Exception as e:
    print("Failed finding longitude, exception:", e)
    print("lon value: ", lat)

尝试1个结果：

.......========.......
IMG_0149.JPG has been successful
.......========.......
IMG_0161.JPG has been successful
.......========.......
IMG_0377.JPG has been successful
.......========.......
Failed finding latitude, exception: could not convert string to float:
lat value:  b''
Failed finding longitude, exception: could not convert string to float:
lon value:  b''

尝试2个结果：

.......========.......
IMG_0149.JPG has been successful
.......========.......
IMG_0161.JPG has been successful
.......========.......
IMG_0377.JPG has been successful
.......========.......
IMG_0007.JPG has been successful
.......========.......
Failed finding lattitude, exception: could not convert string to float:
lat value:  b''
Failed finding longitude, exception: could not convert string to float:
lon value:  b''

Answer 1

这可能是您引用引起麻烦的文件名的方式，或者可能是迈克尔·布彻（Michael Butscher）建议的时机。我尝试自己写一个解决方案，发现我的大多数照片都没有坐标。

这是我的解决方案，请告诉我它是否适合您。请注意，对于那些没有坐标的图片，lat=="(null)"和lon="(null)"。对于具有坐标的坐标，lat和lon将是浮点。

#!/usr/bin/env python3
import pathlib
import subprocess

def main():
    """ Entry """
    for pic_file in pathlib.Path('.').glob('*.jpg'):
        print('-' * 72)
        print(pic_file)
        command = ['mdls',
                   '-name', 'kMDItemLatitude',
                   '-name', 'kMDItemLongitude',
                   str(pic_file)]
        output = subprocess.check_output(command, encoding='utf-8')
        # Sample output
        #    kMDItemLatitude  = (null)
        #    kMDItemLongitude = (null)
        # or
        #    kMDItemLatitude  = 46.75725833333333
        #    kMDItemLongitude = -71.28605666666667        
        print(output)

        # Parse the output
        lines = output.splitlines()
        values = [line.split()[-1] for line in lines]
        print(values)

        # Convert to float
        try:
            lat, lon = [float(value) for value in values]
        except ValueError:
            lat, lon = values

        print('Latitude =', lat)
        print('Logitude =', lon)


if __name__ == '__main__':
    main()

注释

我不使用grep和awk命令，因为我想自己解析值
通常，subprocess函数的输出将返回原始字节数组，我使用encoding='utf-8'将其转换为Python 3字符串。

子进程间歇性返回空

1 个答案:

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