## Applying a Function to Every Row in a pandas DataFrame

Pandas is a powerful tool for data manipulation and analysis in Python. It provides highly efficient data structures that allow for easy handling of data and integration with other Python libraries.

In this article, we will discuss how to apply a function to every row in a pandas DataFrame.

## Basic Syntax for Applying a Function to Every Row

When working with large datasets, it’s common to need to perform the same operation on every row of a DataFrame. Pandas provides several methods for applying a function to every row.

One common method is to use the apply() function, which can be used to apply any function to each row of a DataFrame. The basic syntax for using the apply() function is as follows:

`df.apply(func, axis=1)`

Here, `func`

refers to the function that we want to apply to each row, and `axis=1`

specifies that we want to apply the function row-wise.

### Example: Applying Function to Multiply and Divide Columns

To demonstrate how to apply a function to every row in a pandas DataFrame, let’s consider an example where we want to multiply two columns and divide the result by a third column. We can accomplish this using a lambda function with the apply() function.

```
import pandas as pd
data = {'A': [1, 2, 3, 4, 5],
'B': [2, 2, 3, 3, 4],
'C': [2, 3, 2, 2, 1]}
df = pd.DataFrame(data)
df['D'] = df.apply(lambda x: (x['A']*x['B'])/x['C'], axis=1)
print(df)
```

In the above code, we first create a DataFrame `df`

with three columns ‘A’, ‘B’, and ‘C’. We then use the apply() function with a lambda function to multiply columns ‘A’ and ‘B’ and divide the result by column ‘C’.

Finally, we add the result as a new column ‘D’ to the DataFrame. Output:

```
A B C D
0 1 2 2 1.0
1 2 2 3 1.3
2 3 3 2 4.5
3 4 3 2 6.0
4 5 4 1 20.0
```

As we can see, the apply() function has successfully applied the lambda function to every row of the DataFrame.

## Additional Resources for Performing Common Operations in pandas

In addition to applying a function to every row in a DataFrame, pandas provides several other functions for performing common operations on data. Some of these are listed below:

### Data Import and Export

`read_csv()`

: For reading data from a CSV file.`read_excel()`

: For reading data from an Excel file.`to_csv()`

: For exporting data to a CSV file.

### Data Selection and Filtering

`loc[]`

: For selecting rows and columns by label.`iloc[]`

: For selecting rows and columns by index.- Boolean indexing: For filtering data based on a condition.

### Data Aggregation and Grouping

`groupby()`

: For grouping data by one or more columns.`pivot_table()`

: For creating a pivot table from a DataFrame.- Aggregation functions: For calculating summary statistics on groups of data.

### Data Cleaning and Manipulation

`dropna()`

: For dropping rows or columns with missing values.`fillna()`

: For filling missing values in a DataFrame.`replace()`

: For replacing values in a DataFrame.

### Data Visualization

`plot()`

: For creating various types of plots, such as line, bar, and scatter plots.`scatter()`

: For creating a scatter plot.`histogram()`

: For creating a histogram.

## Conclusion

In this article, we have discussed how to apply a function to every row in a pandas DataFrame using the apply() function.

We have also listed several additional resources for performing common operations in pandas, such as data import and export, data selection and filtering, data aggregation and grouping, data cleaning and manipulation, and data visualization. By using these functions, one can easily manipulate and analyze large datasets in pandas.

In conclusion, this article has discussed the importance of applying functions to every row in a pandas DataFrame, providing basic syntax and an example of a lambda function. Additionally, it has listed several additional resources for performing common operations in pandas, including data import/export, filtering, aggregation, cleaning, and visualization.

The ability to easily manipulate and analyze large datasets in pandas makes it a vital tool for data scientists, researchers, and professionals alike. By knowing how to apply functions to every row and using these additional resources, one can streamline data analysis and achieve meaningful insights in a more efficient manner.