Python – Iterate through list, cleanse string, convert to float and multiply

Question

I have input data which contains strings and I want to convert the elements in the list to a number.

To do this, first I need to remove the word ‘stars’, which I did in the code.

I am stuck in the next step, where I need to remove the letter ‘k’ from elements that has it. Then, for elements originally had a letter ‘k’, I need to multiply its value by 1000.

#Input data
starlist =  [ '1.1k stars', '1k stars', '1k stars', '978 stars']

#Remove the word stars
starlist = [starlist .replace('stars','') for starlist in starlist ]

Expected output

startlist = [‘1100’, ‘1000’, ‘1000’, ‘978’]

I tried creating a for loop to iterate through the list, identify if the element has a ‘k’. If it does, then remove k, convert to float and multiply by 1000. Problem with this approach is, I cannot overwrite the original value in the original list. I’m not sure how to write back into the original list.

#Remove letter 'k' and multiply by 1000 by if the element had letter 'k'
for rating in starlist:
    if rating.find('k') != -1:        
        rating = rating.replace('k','')
        rating = float(rating) * 1000

Asked By: JJH

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Source

Answer 1

#Input data
starlist =  [ '1.1k stars', '1k stars', '1k stars', '978 stars']

#Remove the word stars
starlist = [starlist .replace('stars','') for starlist in starlist ]

newlist = []

#Remove letter 'k' and multiply by 1000 by if the element had letter 'k'
for rating in starlist:
    if rating.find('k') != -1:        
        rating = rating.replace('k','')
        rating = float(rating) * 1000
        newlist.append(rating)
    else:
        rating = float(rating)
        newlist.append(rating)
        
starlist = newlist
print(starlist)

Answered By: Aymen

Answer 2

You were on the right track. Two small things came in:

use the rating to find "k".
consider case where there is no "k".

#Remove letter 'k' and multiply by 1000 by if the element had letter 'k'
mlist = []
for rating in starlist:
    if rating.find('k') != -1:        
        rating = rating.replace('k','')
        rating = float(rating) * 1000
    else:
        rating = float(rating)
    mlist.append(rating)

starlist = mlist
print(starlist)

Answered By: Jib

Answer 3

For simplicity we will define function to convert rating

def convert_rating(rating):
    # Here we found a bug in your code! It should be rating, not starlist
    if rating.find('k') != -1:        
        rating = rating.replace('k','')
        return float(rating) * 1000
    return int(rating)

You have few options here.

Creating new list

starlist = [convert_rating(r) for r in starlist]

Use the index to replace values of original starlist

for index, rating in enumerate(starlist):
    starlist[index] = convert_rating(rating)

One thing more! The floats can be inaccurate, so you should use Decimal or update convert_rating function to remove the comma from string and multiply by proper amount.

Answered By: kosciej16

Answer 4

I provide two methods.

Create a new list, then assign it to the original list.

starlist = [ float(rating.replace('k', ''))*1000 if 'k' in rating else float(rating) for rating in starlist]

Modify the original list in-place by subscripts.

for i, rating in enumerate(starlist):
    starlist[i] = float(rating.replace('k', ''))*1000 if 'k' in rating else float(rating)

Answered By: ILS

Answer 5

# Input data
starlist =  [ '1.1k stars', '1k stars', '1k stars', '978 stars']

# Remove the word stars
starlist = [starlist .replace('stars','') for starlist in starlist ]

The output for your piece of code is:

['1.1k ', '1k ', '1k ', '978 ']

For removing the k, You can loop using enumerate to update a list within a loop.

for i, s in enumerate(starlist):
    if 'k' in s:
        starlist[i] = str(float(s.replace('k', '')) * 1000)

After doing the multiplication with 1000, you can see there is a conversion to str. To have the desired output:

['1100.0', '1000.0', '1000.0', '978 ']

You can lose the str conversion if you aim for having a list of floats.

Answered By: Karim Khaled

Python – Iterate through list, cleanse string, convert to float and multiply

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