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How to Check Column Nulls and Replace: Pandas

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Here is a post that shows how to count Nulls and replace them with the value you want in the Pandas Dataframe. We have explained the process in two steps - Counting and Replacing the Null values. Count null values (column-wise) in Pandas ## count null values column-wise null_counts = df.isnull(). sum() print(null_counts) ``` Output: ``` Column1    1 Column2    1 Column3    5 dtype: int64 ``` In the above code, we first create a sample Pandas DataFrame `df` with some null values. Then, we use the `isnull()` function to create a DataFrame of the same shape as `df`, where each element is a boolean value indicating whether that element is null or not. Finally, we use the `sum()` function to count the number of null values in each column of the resulting DataFrame. The output shows the count of null values column-wise. to count null values column-wise: ``` df.isnull().sum() ``` ##Code snippet to count null values row-wise: ``` df.isnull().sum(axis=1) ``` In the above code, `df` is the Panda

Python placeholder '_' Perfect Way to Use it

What is placeholder in Python? The purpose of it is to mask the variable that you don't want to use in a function. In python, you can call the underscore ( _ ) operator placeholder. Below, you'll find how to use single and double placeholders in a function.


Python placeholder


What is placeholder in python

The purpose of placeholder in Python is to mask variables that you don't want to use in a function. So that your code will be readable. Moreover, in future, if you want to use those variables you can replace the placeholders with the names you want.

In This Page

You'll know in three steps how to use placeholder correctly.
  1. Creating a function
  2. Logic to use single placeholder
  3. Logic to use two placeholders

1. Creating a function.


def function_that_returns_multiple_values(x): 
      return x*2, x*3, x+1 
      for i in range(0,5): 
           square, cube, added_one = function_that_returns_multiple_values(i) 
           print(square, cube)

Here, in print, it returns two variables. I will show you how to mask the unused third variable [added_one] in the below example.

2. Logic to use single placeholder


def function_that_returns_multiple_values(x): 
      return x*2, x*3, x+1 
      for i in range(0,5): 
            square, cube, _ = function_that_returns_multiple_values(i) 
            print(square, cube)

3. Logic to use two placeholders

for i in range(0,5): 
     square, _, _ = function_that_returns_multiple_values(i)


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