How to Efficiently Delete Rows from a Pandas DataFrame Based on a Column Value?

Deleting DataFrame Row in Pandas Based on Column Value

Problem:

Consider a Pandas DataFrame with a column named line_race. The task is to remove all rows where the value in the line_race column is equal to 0.

Efficient Solution:

To efficiently remove rows based on a specific column value, use the following steps:

1. Import the Pandas library:

   import pandas as pd

2. Create the DataFrame with the given data:

   data = {
       "line_race": [11, 11, 9, 10, 10, 9, 8, 9, 11, 8, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
       "rating": [56, 67, 66, 83, 88, 52, 66, 70, 68, 72, 65, 70, 64, 70, 70, -1, -1, -1, -1, -1, 69, -1, -1, -1, -1],
       "rw": [1.000000, 1.000000, 1.000000, 0.880678, 0.793033, 0.636655, 0.581946, 0.518825, 0.486226, 0.446667, 0.164591, 0.142409, 0.134800, 0.117803, 0.113758, 0.109852, 0.098919, 0.093168, 0.083063, 0.075171, 0.048690, 0.045404, 0.039679, 0.034160, 0.030915],
       "wrating": [56.000000, 67.000000, 66.000000, 73.096278, 69.786942, 33.106077, 38.408408, 36.317752, 33.063381, 32.160051, 10.698423, 9.968634, 8.627219, 8.246238, 7.963072, -0.109852, -0.098919, -0.093168, -0.083063, -0.075171, 3.359623, -0.045404, -0.039679, -0.034160, -0.030915],
       "line_date": ["2007-03-31", "2007-03-10", "2007-02-10", "2007-01-13", "2006-12-23", "2006-11-09", "2006-10-22", "2006-09-29", "2006-09-16", "2006-08-30", "2006-02-11", "2006-01-13", "2006-01-02", "2005-12-06", "2005-11-29", "2005-11-22", "2005-11-01", "2005-10-20", "2005-09-27", "2005-09-07", "2005-06-12", "2005-05-29", "2005-05-02", "2005-04-02", "2005-03-13", "2004-11-09"]
   }
   
   df = pd.DataFrame(data)

3. Filter the DataFrame using the query() method, which is faster than using boolean indexing:

   df_filtered = df.query("line_race != 0")

4. Alternatively, you can use the drop() method with the inplace parameter set to True:

   df.drop(df.index[df['line_race'] == 0], inplace=True)

5. The filtered DataFrame can then be assigned to the original DataFrame variable or assigned to a new variable.

The updated DataFrame will no longer contain rows where the line_race column is equal to 0.

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