python和gdal用于图像处理

Question

i have a database catalogue that reads images path as well as other attributes and there is a part that tries to open the dataset in the code so that other processe can go on if the opening was sucessfull but i have hit a stumblimg block as to how to tell the process to go on after the following code, the code runs smoothly but when it encounters an image it can not open it stops instead of going to the begining to read the database again and open a new image.

try:  
    hDataset = gdal.Open( pszFilename, gdal.GA_ReadOnly )  
    except IOError:  
    print("gdalinfo failed - unable to open '%s'." % pszFilename )  
    status = "UPDATE %s SET job = 11  WHERE id = %s" % (table,row[2])  
    setstatus = conn.cursor()  
    setstatus.execute(status)  
    conn.commit()  
    setstatus.close()  
else:  
    print "file opened sucessfully"  
    hDataset.close()

Answer 1

GDAL does not normally throw exceptions, which is a shame. With gdal.UseExceptions() turned on, it sometimes throws RuntimeError (only!), but I haven't found this feature very reliable.

Some functions with GDAL return None if unsuccessful, and others return a status integer, where 0 is good and non-zero is an error code.

A typical form I use is something like this:

hDataset = gdal.Open(pszFilename, gdal.GA_ReadOnly)
if hDataset is None:
    raise IOError("Could not open '%s'" % (pszFilename,))

band_num = 1
band = hDataset.GetRasterBand(band_num)
if band is None:
    raise AttributeError("Raster band %s cannot be fetched" % (band_num,))
...