How can I remove extra whitespace from strings when parsing a csv file in Pandas?

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Question :

How can I remove extra whitespace from strings when parsing a csv file in Pandas?

I have the following file named ‘data.csv’:

    1997,Ford,E350
    1997, Ford , E350
    1997,Ford,E350,"Super, luxurious truck"
    1997,Ford,E350,"Super ""luxurious"" truck"
    1997,Ford,E350," Super luxurious truck "
    "1997",Ford,E350
    1997,Ford,E350
    2000,Mercury,Cougar

And I would like to parse it into a pandas DataFrame so that the DataFrame looks as follows:

       Year     Make   Model              Description
    0  1997     Ford    E350                     None
    1  1997     Ford    E350                     None
    2  1997     Ford    E350   Super, luxurious truck
    3  1997     Ford    E350  Super "luxurious" truck
    4  1997     Ford    E350    Super luxurious truck
    5  1997     Ford    E350                     None
    6  1997     Ford    E350                     None
    7  2000  Mercury  Cougar                     None

The best I could do was:

    pd.read_table("data.csv", sep=r',', names=["Year", "Make", "Model", "Description"])

Which gets me:

    Year     Make   Model              Description
 0  1997     Ford    E350                     None
 1  1997    Ford     E350                     None
 2  1997     Ford    E350   Super, luxurious truck
 3  1997     Ford    E350  Super "luxurious" truck
 4  1997     Ford    E350   Super luxurious truck 
 5  1997     Ford    E350                     None
 6  1997     Ford    E350                     None
 7  2000  Mercury  Cougar                     None

How can I get the DataFrame without those whitespaces?

Asked By: mpjan

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Answer #1:

You could use converters:

import pandas as pd

def strip(text):
    try:
        return text.strip()
    except AttributeError:
        return text

def make_int(text):
    return int(text.strip('" '))

table = pd.read_table("data.csv", sep=r',',
                      names=["Year", "Make", "Model", "Description"],
                      converters = {'Description' : strip,
                                    'Model' : strip,
                                    'Make' : strip,
                                    'Year' : make_int})
print(table)

yields

   Year     Make   Model              Description
0  1997     Ford    E350                     None
1  1997     Ford    E350                     None
2  1997     Ford    E350   Super, luxurious truck
3  1997     Ford    E350  Super "luxurious" truck
4  1997     Ford    E350    Super luxurious truck
5  1997     Ford    E350                     None
6  1997     Ford    E350                     None
7  2000  Mercury  Cougar                     None
Answered By: unutbu

Answer #2:

Adding parameter skipinitialspace=True to read_table worked for me.

So try:

pd.read_table("data.csv", 
              sep=r',', 
              names=["Year", "Make", "Model", "Description"], 
              skipinitialspace=True)

Same thing works in pd.read_csv().

Answered By: TheGrimmScientist

Answer #3:

Well, the whitespace is in your data, so you can’t read in the data without reading in the whitespace. However, after you’ve read it in, you could strip out the whitespace by doing, e.g., df["Make"] = df["Make"].map(str.strip) (where df is your dataframe).

Answered By: BrenBarn

Answer #4:

I don’t have enough reputation to leave a comment, but the answer above suggesting using the map function along with strip won’t work if you have NaN values, since strip only works on chars and NaN are floats.

There is a built-in pandas function to do this, which I used:
pd.core.strings.str_strip(df['Description'])
where df is your dataframe. In my case I used it on a dataframe with ~1.2 million rows and it was very fast.

Answered By: RKD314

Answer #5:

I don’t believe Pandas supported this at the time this question was posted but the the most straight forward way to do this is by using regex in the sep parameter of read_csv. So something like the following should work for this issue.

table = pd.read_table("data.csv", sep=' *, *')
Answered By: Hunter Jackson

Answer #6:

read_table is Deprecated, Here is the message as it appears in the documentation.

Deprecated since version 0.24.0.

Use pandas.read_csv() instead, passing sep=’t’ if necessary.

So using read_csv you can pass in a regex for the sep argument, where you can specify the separator as

sep="s*,s*"

any number of spaces, followed by a separator, followed by any number of space again, this will make sure all the leading and trailing spaces are also chosen as a delimiter chunk which in-turn removes the white-spaces on either side of your data.

regex details as follows:

s -> white-space
* -> any number (zero or many)
, -> no meaning, direct character match

So, the regular expression s*,s* stands for white-space[any number] match a comma and white-space[any number].

if your delimiter is anything else other than a comma then replace the , in the above expression with your delimiter. Eg: s*;s* if ; is your delimiter.

Answered By: Rajshekar Reddy

Answer #7:

Here’s a function to iterate through each column and apply pd.core.strings.str_strip:

def df_strip(df):
  df = df.copy()
  for c in df.columns:
    if df[c].dtype == np.object:
      df[c] = pd.core.strings.str_strip(df[c])
    df = df.rename(columns={c:c.strip()})
  return df
Answered By: J Wang

Answer #8:

The str.strip() function works really well on Series. Thus, I convert the dataframe column that contains the whitespaces into a Series, strip the whitespace using the str.strip() function and then replace the converted column back into the dataframe. Below is the example code.

import pandas as pd
data = pd.DataFrame({'values': ['   ABC   ', '   DEF', '  GHI  ']})
new = pd.Series([])
new = data['values'].str.strip()
data['values'] = new
Answered By: S. Herron

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