String operation performs incorrectly

Question

In main.py i have this

import RemoveShortWords as rs

procLine="the   in  shear flow past a flat plate"
procLine = rs.RemomeOneTwoCharWords(procLine)
print(procLine)

and RemoveShortWords.py is this

def RemomeOneTwoCharWords(procLine):

    procLine = str(procLine)

    for word in procLine.split():

        if(len(word)<=2):
            procLine = procLine.replace(word,"")


    return procLine

print returns this

the sher flow pst flt plte

as you can see function removes words with less than 2 characters. But, for some reason, it removed all "a" characters too. For Example, "flat" became "flt"

Why?

@PM2Ring, sometimes people may miss things. Why not just try to help to explain what's wrong, instead of posting useless comment? — Eric Klaus, Sep 23 '18 at 01:02
@PM2Ring , it is not duplicate, i'm not asking how to remove 2 char words, I asked why code performed not as intended — Eric Klaus, Sep 23 '18 at 01:04
Reopening. The question is about why the code fails; the dupe target did not contain an answer to that question. It may be related, but it's not a dupe. — user2357112, Sep 23 '18 at 01:08

niraj · Accepted Answer · 2018-09-23T00:59:06.663

6

The variable procLine has the in shear flow past a flat plate

And procLine.split() ['the', 'in', 'shear', 'flow', 'past', 'a', 'flat', 'plate']

In for loop, it finds a and replaces a in procLine with empty or removes the character. Note: it would do same if some word was with in e.g. string to strg.

Instead I would suggest something like list comprehension may work:

procLine = ' '.join([w for w in procLine.split() if len(w)>2])

edited Sep 23 '18 at 00:59

answered Sep 23 '18 at 00:55

niraj

17,498
4
33
48

1

oh yes. I missed that somehow. Thank you – Eric Klaus Sep 23 '18 at 00:57
`Happy Coding`. – niraj Sep 23 '18 at 01:05
Why not a generator then? – U13-Forward Sep 23 '18 at 01:24
@U9-Forward There are discussions on comparison of list comprehension and generator comprehension https://stackoverflow.com/questions/11964130/list-comprehension-vs-generator-expressions-weird-timeit-results – niraj Sep 23 '18 at 01:28
@student Okay yeah that's right it's slower, but less memory taken, and two less characters to type, haha – U13-Forward Sep 23 '18 at 01:29
1

@U9-Forward For specific case with `.join` the answer mentions `list comprehension` is better. https://stackoverflow.com/a/9061024/5916727 – niraj Sep 23 '18 at 01:30
1

@student Yeah that's true – U13-Forward Sep 23 '18 at 01:31

score 3 · Answer 2 · edited Jun 20 '20 at 09:12

3

replace replaces all occurrences.

str.replace(old, new[, count])

Return a copy of the string with all occurrences of substring old replaced by new. If the optional argument count is given, only the first count occurrences are replaced.

Documentation

So once the word "a" is reached in the input, procLine.replace("a", "") will remove all "a"s in the entire string. If you only want to replace words shorter than 2 characters, you could use for example list-comprehension:

return ' '.join([s for s in procLine.split(' ') if len(s) > 2])

edited Jun 20 '20 at 09:12

Community

1
1

answered Sep 23 '18 at 00:59

@PM2Ring Interesting; I didn't know that one. Thanks for the info :) I'll edit – Sep 23 '18 at 15:10

score 0 · Answer 3 · answered Jul 01 '21 at 15:10

One thing i think is confusing you is procLine.split() doesn't actually modify procLine.

def RemomeOneTwoCharWords(procLine):
    procLine = str(procLine)
    temp = ""
    for word in procLine.split():
        if len(word)>=2:
            temp += word + " "
    return(temp)
 
procLine="the   in  shear flow past a flat plate"
procLine = RemomeOneTwoCharWords(procLine)
print(procLine)

gives

the shear flow past flat plate

String operation performs incorrectly

3 Answers3