CODEWITHSUNDEEP
pythondictionary
Kalyan
Kalyan

Reputation: 357

Using map function instead of for loop

I want to find number of lines and words in a file. My input file "testfile.txt' has 6 lines and 23 words. For finding number of words I am using map() function instead of the for loop. When I executed this code it shows the memory location of the object instead of "23": Number of words =

What am I doing wrong here?

def wordcount(l):
    global numwords
    words = l.split()
    numwords += len(words)

f=open('testfile.txt')
lines = f.readlines()
numlines = len(lines)
print ('Number of lines =', numlines)

numwords=0

numwords = map(wordcount, lines)
print ('Number of words =', numwords)

Upvotes: 1

Views: 2792

Answers (6)

Gilliland
Gilliland

Reputation: 11

Read paragraphs to lines and ...

print 'Num of words =', reduce(lambda x,y: x+y ,[len(line.split()) for line in lines])

Upvotes: 1

Chris
Chris

Reputation: 435

Here you go, map either returns a list or iterator, so this modification will work in either case. (python2 vs python3) 

def wordcount(l):
    global numwords
    words = l.split()
    numwords += len(words)

f=open('testfile.txt')
lines = f.readlines()
numlines = len(lines)
print ('Number of lines =', numlines)

numwords=0

numwords = map(wordcount, lines)
print ('Number of words =', len(list(numwords)))

Upvotes: 0

user225312
user225312

Reputation: 131647

In Python 3, map is an iterator: (akin: itertools.imap)

class map(object)
 |  map(func, *iterables) --> map object
 |  
 |  Make an iterator that computes the function using arguments from
 |  each of the iterables.  Stops when the shortest iterable is exhausted.

While in Python 2:

map(...)
    map(function, sequence[, sequence, ...]) -> list

It returns a list by default.

So in your case, you need to do:

numwords = list(map(wordcount, lines))

There are other problems also with your code, but others have pointed that out well enough.

Upvotes: 2

Sandro Munda
Sandro Munda

Reputation: 41030

You should avoid to use a global variable like 'numwords'. You have to return numwords in your wordcount() function.

This code works :

def wordcount(l):
    numwords = 0
    words = l.split()
    numwords += len(words)
    return numwords

f = open('testfile.txt')
lines = f.readlines()
numlines = len(lines)
print('Number of lines =', numlines)

numwords = 0
numwords = map(wordcount, lines)
print ('Number of words =', numwords)

My testfile.txt contains :

Hello world
my name is
james bond

Ouput :

('Number of lines =', 3)
('Number of words =', [2, 3, 2])

Upvotes: 1

Dan D.
Dan D.

Reputation: 74645

after:

numwords = map(wordcount, lines)

numwords is a list of None the same length as lines as wordcount returns None

for line in lines:
    words = line.split()
    numwords += len(words)

would be better and more pythonic

Upvotes: 2

Andrey Sboev
Andrey Sboev

Reputation: 7682

function wordcount doesn't return anything, write return numwords Now your function calcualates numwords and then return None by default, and you erase this global variable

Upvotes: 0

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