How can I write an IF statement in Python Pandas to populate a blank column in my dataframe?

user_10252201 0
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I have a column of Results (A, B, C, D or E). In that column are missing values and Not Applicables. I want to insert a new column (done) and in that column if there is a grade between A-E in the Result column, I want to insert that grade in the new column, but if its not A-E, I want to impute a grade randomly in the new column. I want to maintain the integrity of the original Result column. I can impute I think but getting the IF statement bit beforehand is the challenge. I am brand new to this (and an accountant so really have no clue) any help would be much appreciated :)

pandas if-statement python
3 Answers
import random
df['B'] = df['A'].fillna(random.choice(df['A'].dropna().unique().tolist()))

if you only wish to replace nan values with a random result, then this will work. Basically, we fill all the nan values with a randomly chosen result from the first column

'A' is the results column, and 'B' is the new column

user_112800680

You can use fillna

from numpy import NaN
import pandas as pd
import random

choices = ["A", "B", "C", "D", "E"]

df = pd.DataFrame()
df['Result'] = ["A", NaN, "B", "C", NaN]
df['NewColumn'] = df['Result'].fillna(random.choices(choices)[0])
df

Output:

Result  NewColumn
0   A   A
1   NaN E
2   B   B
3   C   C
4   NaN E
user_195328470

@Nicholas answer covers that. I would add that you can also use mapping in case when your na values are somethings else than real na's like for example a string "NotAGrade".

Generally, you could use map like so:

# Mapping titles in titanic dataset
grade_mapping = {"NotAGrade":numpy.random.randint(100)}
df['result_formated'] = df['result'].map(grade_mapping)

Substitute titles mapping and values for desired values.

Also check out this question on how you can use pandas.where and numpy.where in other general situations.

user_131581570
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