Data Analysis Data Wrangling Tutorial
query() method: Query/Filter Columns
- November 24, 2018 • 19 min read
- Key Terms: query, python, pandas
In pandas, we can query the columns of DataFrames with boolean expressions using the query() method. I'll walk through lots of simple examples.
Import Modules¶
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import pandas as pd
import seaborn as sns
Get Flights Data¶
Let's get the flights dataset included in the seaborn library and assign it to the DataFrame df_flights.
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df_flights = sns.load_dataset('flights')
Preview the first few rows of df_flights.
Each row represents a month's flight history details. The passengers column represents that total number of passengers that flew that month.
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df_flights.head()
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This dataset spans 1949 to 1960.
Practice Filtering Rows and Columns¶
Query for rows in which year is equal to 1949¶
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df_flights.query('year==1949')
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Query for rows in which month is equal to January¶
Notice how 'January' is in single quotes because it's a string.
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df_flights.query("month=='January'")
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Query for rows in which year is equal to 1949 and month is equal to January¶
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df_flights.query("year==1949 and month=='January'")
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Query for rows in which month is January or February¶
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df_flights.query("month==['January', 'February']")
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Query for rows in which month equals January and year is less than 1955¶
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df_flights.query("month=='January' and year<1955")
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Query for rows in which month equals January and year is greater than 1955¶
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df_flights.query("month=='January' and year>1955")
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Query for rows in which month equals January and the year is not 1955¶
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df_flights.query("month=='January' and year!=1955")
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Query for rows in which month equals January or year equals 1955¶
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df_flights.query("month=='January' or year==1955")
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