怎么新建MySQL数据库

dict获取关键字与值

values()

>>> d
{'p': 34, 'l': 54, 'b': 88}
>>> for value in d.values():
...     print(value)
...
34
54
88

items()

>>> for key,value in d.items():
...     print(key,value)
...
p 34
l 54
b 88

字典dict(关键字对应的值为list)

方法一

代码

    # 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)

输出

方法二

代码

    # 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)

输出 print(list(pages.items()))的输出

print(pages)的输出