建立字典
建立字典的規則:
- 每個鍵必須是唯一的 (否則它將被覆蓋)
- 每個鍵必須是可雜湊 (可以使用
hash
功能雜湊;否則TypeError
將被丟擲) - 金鑰沒有特定的順序。
# Creating and populating it with values
stock = {'eggs': 5, 'milk': 2}
# Or creating an empty dictionary
dictionary = {}
# And populating it after
dictionary['eggs'] = 5
dictionary['milk'] = 2
# Values can also be lists
mydict = {'a': [1, 2, 3], 'b': ['one', 'two', 'three']}
# Use list.append() method to add new elements to the values list
mydict['a'].append(4) # => {'a': [1, 2, 3, 4], 'b': ['one', 'two', 'three']}
mydict['b'].append('four') # => {'a': [1, 2, 3, 4], 'b': ['one', 'two', 'three', 'four']}
# We can also create a dictionary using a list of two-items tuples
iterable = [('eggs', 5), ('milk', 2)]
dictionary = dict(iterables)
# Or using keyword argument:
dictionary = dict(eggs=5, milk=2)
# Another way will be to use the dict.fromkeys:
dictionary = dict.fromkeys((milk, eggs)) # => {'milk': None, 'eggs': None}
dictionary = dict.fromkeys((milk, eggs), (2, 5)) # => {'milk': 2, 'eggs': 5}