Replacing strings with special characters in pandas dataframe

Question

I'm looking to replace strings inside DataFrame columns, these strings contain special characters.

I tried the following, but nothing changed in the DataFrame:

data = {'col1': ["series ${z_mask0}", "series ${z_mask1}", "series ${z_mask2}"]}

df = pd.DataFrame(data)
print(df)

old_values = ["${z_mask0}", "${z_mask1}", "${z_mask2}"]

new_values = ["${z_00}", "${z_01}", "${z_02}"]

df = df.replace(old_values_sign, new_values_sign, regex=True)
print(df)

The intended output is: ['series ${z_00}', 'series ${z_01}', 'series ${z_02']

Carmoreno · Accepted Answer · 2022-10-25 17:11:56Z

2

You need to escape the $ character using \ in the old_values list:

old_values = ["\${z_mask0}", "\${z_mask1}", "\${z_mask2}"]

The above should be enough. Here is all the code:

old_values = ["\${z_mask0}", "\${z_mask1}", "\${z_mask2}"]
new_values = ["${z_00}", "${z_01}", "${z_02}"]
df = df.replace(old_values, new_values, regex=True)
print(df)

Output:

      col1
0   series ${z_00}
1   series ${z_01}
2   series ${z_02}

edited Oct 25, 2022 at 17:11

answered Oct 25, 2022 at 17:06

Carmoreno

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4 Comments

newuser1628 Over a year ago

Works great if the list is short as the one I posted, but I have a second case where the old_values is too long for me to add "\" manually. I'm editing my question based on your answer

Carmoreno Over a year ago

Well, I think that if your editions are a lot, you should open a new question. :)

newuser1628 Over a year ago

Okay I'll revert my question to how it was and open a new question :)

JRiggles Over a year ago

Out of curiosity, why does escaping work where raw strings don't? I was under the impression that they were (more or less) equivalent.

JRiggles · Accepted Answer · 2022-10-25 16:56:54Z

0

Have you tried using raw strings for the old_values? There are some RegEx characters in there that may be interfering with your result ("{", "}", and "$"). Try this instead:

old_values = [r"${z_mask0}", r"${z_mask1}", r"${z_mask2}"]

Note the r before each string

answered Oct 25, 2022 at 16:56

JRiggles

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1 Comment

newuser1628 Over a year ago

I did try it, but nothing changed as well.

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