Extract int from string in Pandas

Lets say I have a dataframe df as

A B
1 V2
3 W42
1 S03
2 T02
3 U71

I want to have a new column (either at it the end of df or replace column B with it, as it doesn't matter) that only extracts the int from the column B. That is I want column C to look like

C
2
42
3
2
71

So if there is a 0 in front of the number, such as for 03, then I want to return 3 not 03

How can I do this?

Solution 1:

You can convert to string and extract the integer using regular expressions.

df['B'].str.extract('(\d+)').astype(int)

Solution 2:

Assuming there is always exactly one leading letter

df['B'] = df['B'].str[1:].astype(int)

Solution 3:

First set up the data

df = pd.DataFrame({'A': [1, 3, 1, 2, 3], 'B' : ['V2', 'W42', 'S03', 'T02', 'U71']})

df.head()

Then do the extraction and cast it back to ints

df['C'] = df['B'].str.extract('(\d+)').astype(int)

df.head()