CODEWITHSUNDEEP
python
Jassy.W
Jassy.W

Reputation: 539

Python: how to avoid append an empty string in a for loop?

The goal of my codes are to write a function and return a list of strings, in which the successive strings (fruit name) correspond to the consecutive #No.1...#No.5 . The whole name of the fruit was split over multiple lines, and I want to display the fruit name in the list as a single string with no whitespace. I expect my codes return:

['Pear', 'Apple', 'Cherry', 'Banana', 'Peach']

but I got:

['', 'Pear', 'Apple', 'Cherry', 'Banana', 'Peach']

These are the contents of my file fruit.txt:

#NO.1
P
ear
#NO.2
A
pp
l
e
#NO.3
Cherry
#NO.4
Banan
a
#NO.5
Pea
c
h

These are my codes:

def read(filename): 

    myfile = open('fruit', 'r')
    seq = ''
    list1 = []
    for line in myfile:

        if line[0] != '#':
            seq +=line.rstrip('\n')
        else:

            list1.append(seq)
            seq = ''

    list1.append(seq)    
    return list1

how to avoid to append an empty string which is not what I want? I suppose I just need to adjust the position a certain line of codes, any suggestion is appreciated.

Upvotes: 3

Views: 4058

Answers (3)

Hugo G
Hugo G

Reputation: 16516

Quick fix for removing empty strings from a list:

list1 = filter(None, list1)

How about this solution with regex? The following is a two-step process. First all whitespace like newlines, spaces etc. is removed. Then all words following your pattern #No.\d are found:

import re

whitespace = re.compile(r'\s*')
fruitdef = re.compile(r'#NO\.\d(\w*)')
inputfile = open('fruit', 'r').read()

inputstring = re.sub(whitespace, '', inputfile)
fruits = re.findall(fruitdef, inputstring)

print fruits

['Pear', 'Apple', 'Cherry', 'Banana', 'Peach']

Minified to a oneliner:

import re

print re.findall(r'#NO\.\d(\w*)', re.sub(r'\s*', '', open('fruit', 'r').read()))

Upvotes: 1

Oxymoron88
Oxymoron88

Reputation: 495

Alternative if you'd like a single line solution:

with open('fruit.txt') as f:
    content = f.read()

output = [''.join(x.split('\n')[1:len(x.split('\n'))+1]) for x in content.split('#') if len(x.split('\n')) > 1]

Upvotes: 1

NPE
NPE

Reputation: 500683

You could change the

    else:

to

    elif seq:

This checks whether seq is empty and only appends it if it's not.

Upvotes: 4

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