Creating a new dict in Python
我想用python建立一个字典。但是,我看到的所有示例都是从列表中实例化字典等。…
如何在python中创建新的空字典?
不带参数调用
1 | new_dict = dict() |
或者简单地写
1 | new_dict = {} |
你可以做到这一点
1 2 | x = {} x['a'] = 1 |
了解如何编写预设字典也很有用:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | cmap = {'US':'USA','GB':'Great Britain'} def cxlate(country): try: ret = cmap[country] except: ret = '?' return ret present = 'US' # this one is in the dict missing = 'RU' # this one is not print cxlate(present) # == USA print cxlate(missing) # == ? # or, much more simply as suggested below: print cmap.get(present,'?') # == USA print cmap.get(missing,'?') # == ? # with country codes, you might prefer to return the original on failure: print cmap.get(present,present) # == USA print cmap.get(missing,missing) # == RU |
1 2 | >>> dict(a=2,b=4) {'a': 2, 'b': 4} |
将在python字典中添加值。
1 | d = dict() |
或
1 | d = {} |
或
1 2 | import types d = types.DictType.__new__(types.DictType, (), {}) |
因此,有两种方法可以创建dict:
但在这两个选项中,
1 2 3 4 | >>> dict.fromkeys(['a','b','c'],[1,2,3]) {'a': [1, 2, 3], 'b': [1, 2, 3], 'c': [1, 2, 3]} |