isin, between and query

Three ways to say a condition that reads like the question.

isin for a set of values

Testing against several values with a chain of == and | works and reads badly. isin says it once.

import pandas as pd

df = pd.DataFrame({"subject": ["maths", "art", "computing"]})
print(df[df["subject"].isin(["maths", "computing"])].shape)

between for a range

between is inclusive at both ends by default, which is usually what a range in a sentence means.

import pandas as pd

df = pd.DataFrame({"score": [55, 70, 95]})
print(df[df["score"].between(60, 90)]["score"].tolist())

Exercise

Try It Yourself

Write in_subjects(df, subjects) returning the number of rows whose subject is one of subjects.

import pandas as pd

def in_subjects(df, subjects):
    # How many rows are in one of these subjects?
    return 0

print(in_subjects(pd.DataFrame({"subject": ["maths"]}), ["maths"]))

Press Run to see output

Check Your Understanding

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