Python pandas replace string

Question

Given this data frame...:

DF = pd.DataFrame({'COL1': ['A', 'B', 'C', 'D','D','D'], 
                   'COL2': [11032, 1960, 11400, 11355, 8, 7], 
                   'year': ['2016', '2017', '2018', '2019', '2020', '2021']})
DF

   COL1 COL2    year
0   A   11032   2016
1   B   1960    2017
2   C   11400   2018
3   D   11355   2019
4   D   8       2020
5   D   7       2021

If the following conditions are met:

COL1 = 'D'

year = '2021' (please treat it as a string)

Then change the value in COL2 to 100.

Alternatively, what if year is treated as an int?

Alexander · Accepted Answer · 2015-10-07 03:42:47Z

3

This is a typical use case of loc. When selecting multiple criteria for the row selection, an example of a cond 1 and (cond 2 or cond 3) pattern would be df.loc[(condition 1) & ((condition 2) | (condition 3), 'selected columns'].

DF.loc[(DF.COL1 == 'D') & (DF.year == '2021'), 'COL2'] = 100

If the year were an integer, you could simply amend it as follows to capture both integers and strings:

DF.loc[(DF.COL1 == 'D') & (DF.year.astype(int) == 2021), 'COL2'] = 100

edited Oct 7, 2015 at 3:42

answered Oct 7, 2015 at 3:37

Alexander

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3 Comments

Dance Party Over a year ago

What if I wanted to use a column name in place of 'D' and 2021 to iterate through two columns containing values including 'D' and 2021 and change the corresponding value per row in 'COL2'?

Alexander Over a year ago

I'm not sure I follow. Can you post a new question with sample data and desired result?

Dance Party Over a year ago

Sure; posted here: stackoverflow.com/questions/33029505/…

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