[英]Adding a Dict item to a list and appending values having same key to a newer list item
我有以下实现:
from collections import defaultdict
from collections import OrderedDict
prod = [
[1, 'tomato', 'veg', 'Jan-1'],
[1, 'banana', 'fruit', 'Jan-3'],
[2, 'melon', 'fruit', 'Jan-2'],
[3, 'apple', 'fruit', 'Jan-4'],
[2, 'cucumber', 'veg', 'Jan-1']
]
d = defaultdict(list)
for i in range (0, len(prod)):
f_name = prod[i][1]
f_type = prod[i][2]
f_date = prod[i][3]
key = prod[i][0]
d[key].append([f_name, f_type, f_date])
e = OrderedDict(sorted(d.items(), key=lambda t: t[0]))
print ("***************")
print (e)
table_for_graph = []
for key, value in e.iteritems():
table_for_graph.append(value)
print (table_for_graph)
我得到的输出是这样的:
[[['tomato', 'veg', 'Jan-1'], ['banana', 'fruit', 'Jan-3']], [['melon', 'fruit', 'Jan-2'], ['cucumber', 'veg', 'Jan-1']], [['apple', 'fruit', 'Jan-4']]]
我想创建一个像这样的列表:
[
['tomato''\n''banana','veg''\n''fruit','Jan-1''\n''Jan-3'],
['melon''\n''cucumber','fruit''\n''veg','Jan-2''\n''Jan-1'],
['apple','fruit','Jan-4']
]
意思是,我想连接具有相同密钥的项目。 我该怎么办? 我对迭代thorugh dict还不熟悉。
对于初学者来说,构造字典的循环可以大大简化,因为拆包和重新打包是多余的,除非您需要对元素进行重新排序:
for item in prod:
d[item[0]] = item[1:]
其次, table_graph
最初完全不需要循环:
table_for_graph = e.values()
这里的每个项目都是一个嵌套列表,例如:
>>> e[1]
[['tomato', 'veg', 'Jan-1'],
['banana', 'fruit', 'Jan-3']]
您可以通过将位压缩在一起来有效地转置它:
>>> zip(*e[1])
[['tomato', 'banana'],
['veg', 'fruit'],
['Jan-1', 'Jan-3']]
放在一起:
>>> [s in line for line in zip(*e[1]) for s in line]
['tomato', 'banana', 'veg', 'fruit', 'Jan-1', 'Jan-3']
您可以在字典的每个元素上运行该表达式:
table_for_graph = [[s for line in zip(*value) for s in line] for value in e.itervalues()]
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