Creating a sub dataframe from a dataframe based on a column value

Question

I want to create a data frame that only includes av_rating for the title - "Law & Order: Special Victims Unit" from the following CSV file. How can I do that? The following code is giving me the same data as subset instead of just giving only for the title "Law & Order: Special Victims Unit"

import pandas as pd
ratings = pd.read_csv("http://becomingvisual.com/python4data/tv.csv")
ratings
subset = ratings[["title", "av_rating"]]
subset
for i in subset["title"]:
  if i == "Law & Order: Special Victims Unit":  
    subset_1 = subset[["title", "av_rating"]]
subset_1

skchandra · Accepted Answer · 2020-11-02 04:17:47Z

1

@JGM answers the OP's question (with a small change). Filter is to be on title column rather than on av_rating column.


ratings[ratings['title'] == 'Law & Order: Special Victims Unit'][['title','av_rating']]

and .loc method also can be used to filter.


ratings.loc[ratings['title'] == 'Law & Order: Special Victims Unit',  ['title','av_rating'] ]

ratings['title'] == 'Law & Order: Special Victims Unit' is a index filter

['title','av_rating'] is a columns selector

edited Nov 2, 2020 at 4:17

answered Nov 2, 2020 at 2:57

skchandra

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Comments

JGM · Accepted Answer · 2020-11-02 02:12:37Z

First you need to create a filter like this:

filter = ratings.av_rating == 'Law & Order: Special Victims Unit'

The filter is a boolean variable, and return something like:

filter = [True, True, False, True, ... , True, False]

True occures when ratings.av_rating == 'Law & Order: Special Victims Unit' and False occures when ratings.av_rating != 'Law & Order: Special Victims Unit', naturally.

Then, you need to use the filter, to select the values that you want:

final_data = rating[filter]

The variable final_data contains the old data ONLY when filtre == True (ratings.av_rating == 'Law & Order: Special Victims Unit'). Now, to select only title and av_rating:

final_data_titles = final_data[["title", "av_rating"]]

You can use query too:

final_rating = rating.query("av_rating == 'Law & Order: Special Victims Unit'")

Then,

final_data_titles = final_data[["title", "av_rating"]]

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