python中dict获取关键字与值的实现

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>>> d

{'p': 34, 'l': 54, 'b': 88}

>>> for value in d.values():

...     print(value)

...

34

54

88

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>>> for key,value in d.items():

...     print(key,value)

...

p 34

l 54

b 88

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# method 1

pages = {}

page = []

for img_name in os.listdir(args.image_dir):

    pre_str = img_name[:2]

    #print(pre_str)

    if pre_str not in pages.keys():

        tmp_list = []

        tmp_list.append(os.path.join(args.image_dir, img_name))

        pages[pre_str] = tmp_list

    else:

        pages[pre_str].append(os.path.join(args.image_dir, img_name))

print(pages)

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# method 2

from collections import defaultdict

pages = defaultdict(list)

for img_name in os.listdir(args.image_dir):

    pre_str = img_name[:2]

    #print(pre_str)

    pages[pre_str].append(os.path.join(args.image_dir, img_name))

print(list(pages.items()))

print(pages)