使用过滤器替换Python中的搜索功能

Question

To Python lovers and experts,

My code:

def getAssignee(keyTitle):
    assignee = ''
    for item in assigneeList:
        if(item['title']==keyTitle):
            assignee = item['name']
            break
    return assignee

My intention: To try out filter in python and replace above code with filter function. Assignee list is a list of dictionaries. Eg

assigneeList = [{'title':'Book', 'name':'Davis'},{'title':'TV','name':'Samsung'}]

My reference: Most efficient way to search in list of dicts

My attempt:

assignee = filter(lambda item: item['title']=='TV',assigneeList)
print(assignee['name'])

My Output: Not working. Error "Value 'assignee' is unsubscriptable"

My question: How to get the assignee name, like how I got from the getAssignee() function?

Answer 1

The result of filter is a filter object, you can handle this several ways, and handling the eventuality of an empty filter

• use next(.., None) to get first matching or None value

  def getAssignee(keyTitle): assignee = next(filter(lambda item: item['title'] == keyTitle, assigneeList), None) return assignee['name'] if assignee else ''

• collect the items in a list then pic the first

  def getAssignee(keyTitle): assignee = list(filter(lambda item: item['title'] == keyTitle, assigneeList)) return assignee[0]['name'] if assignee else ''

The next solution if more performant as it don't generates all the filter object, (the list will consumes all the filter, and eventually it could be big)

Answer 2

>>> assignee = filter(lambda item: item['title']=='TV',assigneeList)
>>> type(assignee)
<class 'filter'>

In python 3 filter function will return filter object. filter(function, iterable) is equivalent to the generator expression (item for item in iterable if function(item)) . So In order to evaluate the items you can call list(assignee)