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Taiguara Cavaliere
Taiguara Cavaliere

Reputation: 47

Loop to remove prefix in dataframe

I have a DF where some values have a prefix and I want to make a loop to remove it. The DF looks like this: enter image description here

I want to remove the "null-" and just leave the numbers. I tried that, but I got and error message: enter image description here

Upvotes: 1

Views: 538

Answers (3)

constantstranger
constantstranger

Reputation: 9379

Like this:

df = df.applymap(lambda x: x if type(x) is not str or not x.startswith('null-') else x[len('null-'):])

Explanation:

  • applymap() applies a function to every element in the DataFrame.
  • The lambda above will work for heterogeneous data types (mix of numbers and strings, for example)

UPDATE:

Here's a benchmarking comparison of my applymap() based solution with a replace() solution such as the one in the answer by @wwnde:

enter image description here

As the image above shows, replace() is faster for very small dataframes (on the order of 100-1000 items), but for larger dataframes the applymap() approach is the winner.

Upvotes: 2

wwnde
wwnde

Reputation: 26676

Use dataframe replace

 df = df.replace(to_replace=r'null-', value='', regex=True)

Upvotes: 2

MoRe
MoRe

Reputation: 2372

df.apply(lambda x: x.str.replace("null-",""))

or, if you only want to remove from start:

df.apply(lambda x: x.str.lstrip("null-"))

Upvotes: 1

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