CODEWITHSUNDEEP
pythonregexpandasnltk
imanexcelnoob
imanexcelnoob

Reputation: 1343

re.sub erroring with "Expected string or bytes-like object"

I have read multiple posts regarding this error, but I still can't figure it out. When I try to loop through my function:

def fix_Plan(location):
    letters_only = re.sub("[^a-zA-Z]",  # Search for all non-letters
                          " ",          # Replace all non-letters with spaces
                          location)     # Column and row to search    

    words = letters_only.lower().split()
    stops = set(stopwords.words("english"))
    meaningful_words = [w for w in words if not w in stops]
    return (" ".join(meaningful_words))

col_Plan = fix_Plan(train["Plan"][0])
num_responses = train["Plan"].size
clean_Plan_responses = []

for i in range(0,num_responses):
    clean_Plan_responses.append(fix_Plan(train["Plan"][i]))

Here is the error:

Traceback (most recent call last):
  File "C:/Users/xxxxx/PycharmProjects/tronc/tronc2.py", line 48, in <module>
    clean_Plan_responses.append(fix_Plan(train["Plan"][i]))
  File "C:/Users/xxxxx/PycharmProjects/tronc/tronc2.py", line 22, in fix_Plan
    location)  # Column and row to search
  File "C:\Users\xxxxx\AppData\Local\Programs\Python\Python36\lib\re.py", line 191, in sub
    return _compile(pattern, flags).sub(repl, string, count)
TypeError: expected string or bytes-like object

Upvotes: 132

Views: 551073

Answers (6)

Mostafa
Mostafa

Reputation: 999

I had the same problem. And it's very interesting that every time I did something, the problem was not solved until I realized that there were two special characters in the string.

For example, for me, the text has two characters:

&lrm; (Left-to-Right Mark) and &zwnj; (Zero-width non-joiner)

The solution for me was to delete these two characters and the problem was solved.

import re
mystring = "&lrm;Some Time W&zwnj;e"
mystring  = re.sub(r"&lrm;", "", mystring)
mystring  = re.sub(r"&zwnj;", "", mystring)

I hope this has helped someone who has a problem like me.

Upvotes: 4

cottontail
cottontail

Reputation: 23081

Use str.replace instead

This is about 7 years too late for OP but if you got here because you got a similar error by using re.sub on a pandas column, consider using str.replace built into pandas instead. The reason is that the most common reason this error pops up is when a pandas column contains (unexpected) NaN values in it which re.sub cannot handle whereas str.replace handles it under the hood for us.

Example:

train = pd.DataFrame({'Plan': ["th1s", '1s', 'N01ce', 'and', float('nan')]})

[re.sub("[^a-zA-Z]", " ", x) for x in train['Plan']]      # <--- TypeError: expected string or bytes-like object
train['Plan'].str.replace(r"[^a-zA-Z]", " ", regex=True)  # <--- OK

Now for OP, their fix_Plan function does more than just replacing strings; however, we can still do all of that in a vectorized way as follows (more or less replace re functions by its pandas counterparts).

stops = set(stopwords.words("english"))
stop_words = '|'.join(fr"\b{w}\b" for w in stops)  # pattern to catch stop words
clean_Plan_responses = (
    train['Plan']
    .str.replace("[^a-zA-Z]", " ", regex=True)     # replace all non-letters with spaces
    .str.lower()                                   # convert to lower case
    .str.replace(stop_words, "", regex=True)       # remove all stop words
    .str.split().str.join(" ")                     # remove extraneous space characters
)

Upvotes: 1

stay_funn
stay_funn

Reputation: 15

from my experience in Python, this is caused by a None value in the second argument used in the function re.findall().

import re
x = re.findall(r"\[(.*?)\]", None)

One reproduce the error with this code sample.

To avoid this error message, one can filter the null values or add a condition to put them out of the processing

Upvotes: 0

msaif
msaif

Reputation: 291

The simplest solution is to apply Python str function to the column you are trying to loop through.

If you are using pandas, this can be implemented as:

dataframe['column_name']=dataframe['column_name'].apply(str)

Upvotes: 29

Bilal Chandio
Bilal Chandio

Reputation: 89

I suppose better would be to use re.match() function. here is an example which may help you.

import re
import nltk
from nltk.tokenize import word_tokenize
nltk.download('punkt')
sentences = word_tokenize("I love to learn NLP \n 'a :(")
#for i in range(len(sentences)):
sentences = [word.lower() for word in sentences if re.match('^[a-zA-Z]+', word)]  
sentences

Upvotes: 0

Taku
Taku

Reputation: 33714

As you stated in the comments, some of the values appeared to be floats, not strings. You will need to change it to strings before passing it to re.sub. The simplest way is to change location to str(location) when using re.sub. It wouldn't hurt to do it anyways even if it's already a str.

letters_only = re.sub("[^a-zA-Z]",  # Search for all non-letters
                          " ",          # Replace all non-letters with spaces
                          str(location))

Upvotes: 175

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