Pandas DataFrame.loc[] Method

Pandas DataFrame is a two-dimensional size-mutable, potentially heterogeneous tabular data structure with labeled axes (rows and columns). Arithmetic operations align on both row and column labels. It can be thought of as a dict-like container for Series objects. This is the primary data structure of the Pandas. 

Pandas DataFrame loc[] Syntax

Pandas DataFrame.loc attribute accesses a group of rows and columns by label(s) or a boolean array in the given Pandas DataFrame.

Syntax: DataFrame.loc 

Parameter : None 

Returns : Scalar, Series, DataFrame

Pandas DataFrame loc Property

Below are some examples by which we can use Pandas DataFrame loc[]:

Example 1: Select a Single Row and Column By Label using loc[]

Use DataFrame.loc attribute to access a particular cell in the given Pandas Dataframe using the index and column labels. We are then selecting a single row and column by label using loc[].

# importing pandas as pd
import pandas as pd

# Creating the DataFrame
df = pd.DataFrame({'Weight': [45, 88, 56, 15, 71],
                   'Name': ['Sam', 'Andrea', 'Alex', 'Robin', 'Kia'],
                   'Age': [14, 25, 55, 8, 21]})

# Create the index
index_ = ['Row_1', 'Row_2', 'Row_3', 'Row_4', 'Row_5']

# Set the index
df.index = index_

# Print the DataFrame
print("Original DataFrame:")
print(df)

# Corrected selection using loc for a specific cell
result = df.loc['Row_2', 'Name']

# Print the result
print("\nSelected Value at Row_2, Column 'Name':")
print(result)

Output

Original DataFrame:
       Weight    Name  Age
Row_1      45     Sam   14
Row_2      88  Andrea   25
Row_3      56    Alex   55
Row_4      15   Robin    8
Row_5      71     Kia   21
Selected Value at Row_2, Column 'Name':
Andrea

Example 2: Select Multiple Rows and Columns

Use DataFrame.loc attribute to return two of the column in the given Dataframe and then selecting multiple rows and columns as done in the below example.

# importing pandas as pd
import pandas as pd

# Creating the DataFrame
df = pd.DataFrame({"A":[12, 4, 5, None, 1],
                "B":[7, 2, 54, 3, None],
                "C":[20, 16, 11, 3, 8],
                "D":[14, 3, None, 2, 6]})

# Create the index
index_ = ['Row_1', 'Row_2', 'Row_3', 'Row_4', 'Row_5']

# Set the index
df.index = index_

# Print the DataFrame
print("Original DataFrame:")
print(df)

# Corrected column names ('A' and 'D') in the result
result = df.loc[:, ['A', 'D']]

# Print the result
print("\nSelected Columns 'A' and 'D':")
print(result)

Output

Original DataFrame:
         A    B   C    D
Row_1  12.0   7  20  14.0
Row_2   4.0   2  16   3.0
Row_3   5.0  54  11   NaN
Row_4   NaN   3   3   2.0
Row_5   1.0 NaN   8   6.0
Selected Columns 'A' and 'D':
         A    D
Row_1  12.0  14.0
Row_2   4.0   3.0
Row_3   5.0   NaN
Row_4   NaN   2.0
Row_5   1.0   6.0

Example 3: Select Between Two Rows or Columns

In this example, we creates a pandas DataFrame named 'df', sets custom row indices, and then uses the loc accessor to select rows between 'Row_2' and 'Row_4' inclusive and columns 'B' through 'D'. The selected rows and columns are printed, demonstrating the use of label-based indexing with loc.

# importing pandas as pd
import pandas as pd

# Creating the DataFrame
df = pd.DataFrame({"A": [12, 4, 5, None, 1],
                   "B": [7, 2, 54, 3, None],
                   "C": [20, 16, 11, 3, 8],
                   "D": [14, 3, None, 2, 6]})

# Create the index
index_ = ['Row_1', 'Row_2', 'Row_3', 'Row_4', 'Row_5']

# Set the index
df.index = index_

# Print the original DataFrame
print("Original DataFrame:")
print(df)

# Select Rows Between 'Row_2' and 'Row_4'
selected_rows = df.loc['Row_2':'Row_4']
print("\nSelected Rows:")
print(selected_rows)

# Select Columns 'B' through 'D'
selected_columns = df.loc[:, 'B':'D']
print("\nSelected Columns:")
print(selected_columns)

Output

Original DataFrame:
         A    B   C    D
Row_1  12.0   7  20  14.0
Row_2   4.0   2  16   3.0
Row_3   5.0  54  11   NaN
Row_4   NaN   3   3   2.0
Row_5   1.0 NaN   8   6.0
Selected Rows:
        A  B   C    D
Row_2   4  2  16   3.0
Row_3   5  54  11   NaN
Row_4 NaN   3   3   2.0
Selected Columns:
        B   C    D
Row_1   7  20  14.0
Row_2   2  16   3.0
Row_3  54  11   NaN
Row_4   3   3   2.0
Row_5 NaN   8   6.0

Example 4: Select Alternate Rows or Columns

In this example, we creates a pandas DataFrame named 'df', sets custom row indices, and then uses the iloc accessor to select alternate rows (every second row) and alternate columns (every second column). The resulting selections are printed, showcasing the use of integer-based indexing with iloc.

# importing pandas as pd
import pandas as pd

# Creating the DataFrame
df = pd.DataFrame({"A": [12, 4, 5, None, 1],
                   "B": [7, 2, 54, 3, None],
                   "C": [20, 16, 11, 3, 8],
                   "D": [14, 3, None, 2, 6]})

# Create the index
index_ = ['Row_1', 'Row_2', 'Row_3', 'Row_4', 'Row_5']

# Set the index
df.index = index_

# Print the original DataFrame
print("Original DataFrame:")
print(df)

# Select Alternate Rows
alternate_rows = df.iloc[::2]
print("\nAlternate Rows:")
print(alternate_rows)

# Select Alternate Columns
alternate_columns = df.iloc[:, ::2]
print("\nAlternate Columns:")
print(alternate_columns)

Output

Original DataFrame:
         A    B   C    D
Row_1  12.0   7  20  14.0
Row_2   4.0   2  16   3.0
Row_3   5.0  54  11   NaN
Row_4   NaN   3   3   2.0
Row_5   1.0 NaN   8   6.0
Alternate Rows:
        A    B   C    D
Row_1  12.0   7  20  14.0
Row_3   5.0  54  11   NaN
Row_5   1.0 NaN   8   6.0
Alternate Columns:
         A   C
Row_1  12.0  20
Row_2   4.0  16
Row_3   5.0  11
Row_4   NaN   3
Row_5   1.0   8

Example 5: Using Conditions with Pandas loc

In this example, we are creating a pandas DataFrame named 'df', sets custom row indices, and utilizes the loc accessor to select rows based on conditions. It demonstrates selecting rows where column 'A' has values greater than 5 and selecting rows where column 'B' is not null. The resulting selections are then printed, showcasing the use of conditional filtering with loc.

# importing pandas as pd
import pandas as pd

# Creating the DataFrame
df = pd.DataFrame({"A": [12, 4, 5, None, 1],
                   "B": [7, 2, 54, 3, None],
                   "C": [20, 16, 11, 3, 8],
                   "D": [14, 3, None, 2, 6]})

# Create the index
index_ = ['Row_1', 'Row_2', 'Row_3', 'Row_4', 'Row_5']

# Set the index
df.index = index_

# Print the original DataFrame
print("Original DataFrame:")
print(df)

# Using Conditions with loc
# Example: Select rows where column 'A' is greater than 5
selected_rows = df.loc[df['A'] > 5]
print("\nRows where column 'A' is greater than 5:")
print(selected_rows)

# Example: Select rows where column 'B' is not null
non_null_rows = df.loc[df['B'].notnull()]
print("\nRows where column 'B' is not null:")
print(non_null_rows)

Output

Original DataFrame:
         A    B   C    D
Row_1  12.0   7  20  14.0
Row_2   4.0   2  16   3.0
Row_3   5.0  54  11   NaN
Row_4   NaN   3   3   2.0
Row_5   1.0 NaN   8   6.0
Rows where column 'A' is greater than 5:
         A   B   C    D
Row_1  12.0   7  20  14.0
Row_3   5.0  54  11   NaN
Rows where column 'B' is not null:
         A  B   C    D
Row_1  12.0  7  20  14.0
Row_2   4.0  2  16   3.0
Row_3   5.0  54  11   NaN
Row_4   NaN  3   3   2.0