Replace function with pythons built in map function

Question

Problem : I want to improve my understanding of the python map function. I made a function which can return the lengths of words in a given phrase as a list. However, I would like to simply use the map function with a lambda function and pass in a string. Also, I am using python 3.

Current Function (WORKS) :

phrase = 'How long are the words in this phrase'

def word_lengths(phrase):
    phrase = phrase.split(' ')
    wordLengthList = []
    for i in range(len(phrase)):
        wordLengthList.append(len(phrase[i]))
    return wordLengthList

word_lengths(phrase)

Current implementation of map (DOES NOT WORK):

 list(map(lambda x: len(x.split(' ')), phrase))

If anyone could help me resolve this issue I would really appreciate it.

Please update your question to fix the indenting. Python is very sensitive to indenting, as are python programmers. — quamrana
– quamrana, Commented Feb 5, 2018 at 13:30
Generally speaking, map is a little outdated and you might be better off using a list comprehension or a generator expression. Plus personally I find them more readable. — Tom Dalton
– Tom Dalton, Commented Feb 5, 2018 at 13:31
Are you looking for just map(len, phrase.split(' '))? Hard to tell, because your Current Function (WORKS) - actually doesn't (lst is undefined). — Lukas Graf
– Lukas Graf, Commented Feb 5, 2018 at 13:31
Why on earth would you even want to use list(map(lambda... instead of a list comprehension? — Stefan Pochmann
– Stefan Pochmann, Commented Feb 5, 2018 at 13:44

jpp · Accepted Answer · 2018-02-05 13:57:56Z

3

You need to split the input parameter for the phrase variable.

print(list(map(lambda x: len(x), phrase.split(" "))))

Output:

[3, 4, 3, 3, 5, 2, 4, 6]

From the comments: better way of doing it. Thanks Lukas Graf.

print(list(map(len, phrase.split(" ")))

edited Feb 5, 2018 at 13:57

jpp

166k37 gold badges301 silver badges362 bronze badges

answered Feb 5, 2018 at 13:31

Rakesh

82.9k17 gold badges85 silver badges122 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Lukas Graf Over a year ago

That lambda x: len(x) is completely redundant. -> map(len, phrase.split(' '))

Rakesh Over a year ago

@LukasGraf; You are right. I was just helping the OP's original problem :).

Ma0 Over a year ago

@LukasGraf and so is the space to split; it's the default and can be omitted.

Lukas Graf Over a year ago

@Ev.Kounis no, the default is basically "any whitespace", which includes newlines. Slightly different semantics.

jpp · Accepted Answer · 2018-02-05 14:09:54Z

Here are 4 pieces of code for your logic.

I've added the map without lambda as this is most efficient, and also a list comprehension variety as many consider this most pythonic. Timings are indicative only.

phrase = 'How long are the words in this phrase'

def word_lengths(phrase):
    phrase = phrase.split(' ')
    wordLengthList = []
    for i in range(len(phrase)):
        wordLengthList.append(len(phrase[i]))
    return wordLengthList

def word_lengths_map(phrase):
    return list(map(len, phrase.split(' ')))

def word_lengths_lambda(phrase):
    return list(map(lambda x: len(x), phrase.split(' ')))

def word_lengths_lcomp(phrase):
    return [len(x) for x in phrase.split(' ')]

word_lengths(phrase)         # 4.5 microseconds
word_lengths_map(phrase)     # 2.3 microseconds
word_lengths_lambda(phrase)  # 4.0 microseconds
word_lengths_lcomp(phrase)   # 2.8 microseconds
# [3, 4, 3, 3, 5, 2, 4, 6]

AntiMatterDynamite · Accepted Answer · 2018-02-05 13:32:37Z

0

doing this list(map(lambda x: len(x.split(' ')), phrase)) will make map go through each element of phrase (which is a single character), and it will split each of those 1 characters by ' ' (thus creating arrays of length 1)

you should instead split the entire phrase:

list(map(len, phrase.split(' ')))

answered Feb 5, 2018 at 13:32

AntiMatterDynamite

1,5129 silver badges18 bronze badges

1 Comment

AntiMatterDynamite Over a year ago

@StefanPochmann you are right but there is no point in editing the answer

taurus05 · Accepted Answer · 2018-02-05 13:35:55Z

-1

Use map function as follows:

list(map(lambda word: len(word),phrase))

it works perfectly.there is no need to split the word again once we have it.

answered Feb 5, 2018 at 13:35

taurus05

2,56420 silver badges31 bronze badges

Collectives™ on Stack Overflow

Replace function with pythons built in map function

4 Answers 4

4 Comments

Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

4 Comments

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related