Usage of Lambda Functions

Lambda functions are typically used while invoking those functions which take functions as arguments. Here are some of the functions which take other functions as arguments.

  • filter

  • map

  • sorted or sort and more

There are many Python modules which have functions which take other functions as arguments. We will see quite a lot of examples in upcoming chapters.

filter?

map?

sorted?

users = [
    '1,Bryn,Eaken,beaken0@cbc.ca,Female,236.34.175.186',
    '2,Smith,Combe,scombe1@xing.com,Male,',
    '3,Roland,Wallentin,rwallentin2@aboutads.info,Male,94.67.195.44',
    '4,Charlotta,Richten,crichten3@wikia.com,Female,202.51.201.1',
    '5,Berne,Coyne,bcoyne4@squarespace.com,,150.246.120.53',
    '6,Kesley,Hakonsen,khakonsen5@cbc.ca,Female,227.61.48.174',
    "7,Gray,M'Barron,gmbarron6@altervista.org,Male,190.128.200.183",
    '8,Melinde,Scarf,mscarf7@diigo.com,Female,134.41.141.5',
    '9,Arturo,Warkup,awarkup8@nifty.com,Male,',
    '10,Annette,Lowthorpe,alowthorpe9@marketwatch.com,Female,63.157.95.191',
    '11,Melinda,McOwen,mmcowena@unblog.fr,Female,73.95.183.60',
    '12,Minnie,Andrivel,mandrivelb@storify.com,,131.194.233.209',
    '13,Taryn,Medhurst,tmedhurstc@ebay.co.uk,Female,65.191.102.59',
    '14,Fanni,Whitley,fwhitleyd@who.int,Female,184.210.235.118',
    '15,Jareb,Thunderchief,jthunderchiefe@arizona.edu,Male,150.159.27.112',
    '16,Sharona,Haffard,shaffardf@kickstarter.com,Female,91.125.183.157',
    '17,Pattin,Basant,pbasantg@gov.uk,Male,162.227.228.164',
    '18,Beatrice,Butler,bbutlerh@abc.net.au,Female,139.49.169.236',
    '19,Linoel,Bucktrout,lbucktrouti@google.ru,Male,18.17.136.105',
    '20,Katee,Aveyard,kaveyardj@feedburner.com,Female,60.25.33.89'
]

type(users)

type(users[0])

males = filter(
    lambda user: user.split(',')[4] == 'Male',
    users
)
list(males)

male_and_females = filter(
    lambda user: user.split(',')[4] in ('Male', 'Female'),
    users
)
list(male_and_females)

male_and_females = filter(
    lambda user: user.split(',')[4] in ('Male', 'Female'),
    users
)
len(list(male_and_females))

users

user_ips = map(
    lambda user: (int(user.split(',')[0]), user.split(',')[-1]),
    users
)
list(user_ips)

sort_by_gender_and_id = sorted(
    users, 
    key=lambda user: (user.split(',')[4], int(user.split(',')[0]))
)
sort_by_gender_and_id
Lambda Functions Exercise - User Defined Functions