Pandas: How to replace values in a column using for loop if conditions are met

Question

I'm having trouble changing values in a column using for loops if certain conditions are met.

Just a simple example, let's a we have a column of numbers, and I want to replace all numbers less than a 5 into some string like "Hello". How can I do this? I saw .iterrows() and and .set_value() but I'm not sure how to exactly code the for loop-if statement.

This is for Python/pandas

Answer 1

I assume you are using pandas as per the title.

import pandas as pd

df_series = pd.Series(data=[4, 1, -5, 6, 6, 7, 9, 8, 4, -5], index=range(10), name='Column1')
df_series[df_series < 5] = 'Hello'

Note: mixed types are not recommended in columns. The above code will change the type of the column from 'int64' to 'object'.