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abhilash

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

The ** first_valid_index method** is used to return the index for the first non-NA or

`None`

value. The method returns `None`

for the following conditions:- If all elements are non-NA or
`None`

. - If the DataFrame is empty.

Note:Click here to learn more about the pandas library.

```
DataFrame.first_valid_index()
```

The method has no parameters.

import pandas as pdimport numpy as npdef index(dataframe):print("DataFrame is:")print(dataframe)print("Index of the first non-NA/null value is - ", dataframe.first_valid_index())df = pd.DataFrame([[np.nan, np.nan, np.nan],[np.nan, 100,3],[1, 2, 3],[np.nan,-7,np.nan],[-9, -8, -7],[10, 8, 12]],columns=list('XYZ'))df1 = pd.DataFrame([[np.nan, np.nan, np.nan],[np.nan, np.nan, np.nan],[np.nan, np.nan, np.nan],[np.nan,-3,np.nan],[10, 8, 12]],columns=list('XYZ'))df2 = pd.DataFrame([[np.nan, np.nan, np.nan],[np.nan, np.nan, np.nan],[np.nan, np.nan, np.nan]],columns=list('XYZ'))index(df)index(df1)index(df2)

- Lines 1-2: We import the
`pandas`

and`numpy`

modules. - Lines 4–7: We define a function called
`index`

that accepts a DataFrame, prints it, and finds the first non-NA/null value index using the`first_valid_index`

method. - Lines 10–12: We define three different DataFrames with different patterns.
- Lines 14–16: We call the
`index`

method with different DataFrames.

- The output for
`df`

indicates that the 1st row has a non-NA/non-null value in its columns. - The output for
`df1`

indicates that the 3rd row has a non-NA/non-null value in its columns. - The output for
`df2`

indicates that none of the rows have a non-null/non-NA value.

RELATED TAGS

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CONTRIBUTOR

abhilash

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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