字典无法调用键

Question

It's the first time I'm using dictionary in python and I'm not sure if the output is correct as it differs from other results i've seen on here and in examples.

I'm trying to fill a dictionary with a for loop like:

data = {}
i=0

for fe in all_files:
    hdf_file = gdal.Open(workdir1 + "/" + fe)
    subDatasets = hdf_file.GetSubDatasets()
    Emissiv_Bands = gdal.Open(subDatasets[2][0])
    Bands = Emissiv_Bands.ReadAsArray()
    L_B_1 = radiance_scales[specific_band_1] * (Bands[specific_band_1] - radiance_offsets[specific_band_1])
    get_name_tag = re.findall(".A(\d{7}).", all_files[i])
    data ['%s' % get_name_tag] = L_B_1
    i=i+1

with open(workdir1 + "/data_dic.txt", "w") as f1:
    for x,y in data.items():
        print >> f1, x,y
f1.close()

The code is opening files with a specific name and retrieves certain data from it. L_B_1 is just a unit conversion.

So in the line:

data ['%s' % get_name_tag] = L_B_1

I'm trying to fill my dictionary with the name tag as key followed by the value of L_B_1. The print file code below produces this output:

['2018034'] [[ 8.92065776  8.90764162  8.91219727 ...,  8.07265598  8.07265598
   8.07330679]
 [ 8.89202225  8.8698948   8.85232301 ...,  8.0648463   8.0648463
   8.0739576 ]
 [ 8.8874666   8.85687866  8.80936973 ...,  8.07916405  8.07916405
   8.07916405]
 ..., 
 [ 2.43015756  1.97068768  1.78585843 ...,  7.58194735  7.6489805
   7.68477489]
 [ 2.36898168  1.94986185  1.73444466 ...,  7.586503    7.65418695
   7.68152086]
 [ 2.3709341   2.02079983  1.79757296 ...,  7.58845543  7.65548857
   7.67371117]]
['2018194'] [[  7.2610994    6.40789117   5.49936431 ...,   7.96722522   7.90084288
    7.93208163]
 [  7.35741887   6.46451139   5.54557163 ...,   7.98089217   7.96332037
    7.95420907]
 [  7.35741887   6.50421063   5.69265405 ...,   7.98284459   7.97373329
    7.97373329]
 ..., 

Now trying to print for example just the first values:

print data['2018034']

I'm getting:

  Traceback (most recent call last):
      File "MODIS_Plot.py", line 108, in <module>
        print data['2018034']
    KeyError: '2018034'

Why is that? And why is there no format like I see on other pages:

>>Output
{'iphone 3G': 2008, 'iphone 4S': 2011, 'iphone 3GS': 2009, '
    iphone': 2007, 'iphone 5': 2012, 'iphone 4': 2010}

Do I have to put the : behind the keys?

Answer 1

The keys of data come from get_name_tag , whose values come from the result of the re.findall method, which returns a list of matching substrings with 1 capture group in you regex, which is why get_name_tag , as a list, gets converted to ['2018034'] when it is formatted with '%s' % get_name_tag .

Change:

get_name_tag = re.findall(".A(\d{7}).", all_files[i])

to:

get_name_tag = re.findall(".A(\d{7}).", all_files[i])[0]

and your code would work as expected.