python - Lambda Replace

Question

What other approach can I use instead of 'lambda'

def calculate_fees(self):
    return sum(map(lambda x: x.fee, self.bookings.values()))

def calculate_donations(self):
    return sum(map(lambda x: x.donation, self.bookings.values()))

def __str__(self):
    output = 'Event: {0} {1} {2}\n'.format(self.event_id, self.event_date, self.venue) + \
             'Miles: {0}\n'.format(self.miles) + \
             'Max Places: {0}\n'.format(self.max_places) + \
             'Basic Fee: £{0}'.format(self.basic_fee)

    if self.bookings:
        output += '\nRunners:\n' + \
                  '\n'.join(map(lambda x: '{0} {1}'.format(x.runner_id, x.club_id), self.bookings.values()))
    return output

user5547025 · Accepted Answer · 2016-05-24 14:33:24Z

6

The first occurence of lambda could be replaced with a generator:

return sum(x.fee for x in self.bookings.values())

Similar for the second:

return sum(x.donation for x in self.bookings.values())

The third:

'\n'.join('{0} {1}'.format(x.runner_id, x.club_id) for x in self.bookings.values())

Since sum and string.join can deal with a generator, you can use the generator expression directly as an argument to these functions.

answered May 24, 2016 at 14:33

user5547025

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Community · Accepted Answer · 2017-05-23 11:51:40Z

4

Use a generator:

return sum(x.fee for x in self.bookings.values())

Generally, generators and comprehensions improve readability, especially if you have to use a lambda to make map or filter work. Moreover, map and lambda don't play well together performance-wise (Python List Comprehension Vs. Map).

edited May 23, 2017 at 11:51

CommunityBot

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answered May 24, 2016 at 14:33

user2390182

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1 Comment

user2390182 Over a year ago

@polku Thx for attention! Updated my answer.

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