Informatics Practices
Given a dataframe df as shown below :
| A | B | D | |
|---|---|---|---|
| 0 | 15 | 17 | 19 |
| 1 | 16 | 18 | 20 |
| 2 | 20 | 21 | 22 |
What will be the result of following code statements ?
(a) df['C'] = np.NaN
(b) df['C'] = [2, 5]
(c) df['C'] = [12, 15, 27]
Python Pandas
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Answer
(a) df['C'] = np.NaN — This statement will add a new column 'C' to the dataframe and assign np.NaN (Not a Number) to all rows in this new column.
The updated dataframe will look like this:
Output
A B D C
0 15 17 19 NaN
1 16 18 20 NaN
2 20 21 22 NaN
(b) df['C'] = [2, 5] — This statement will result in error because the length of the list [2, 5] does not match the number of rows in the DataFrame df.
(c) df['C'] = [12, 15, 27] — This statement will add a new column 'C' to the dataframe and assign the values from the list [12, 15, 27] to the new column. This time, all rows in the new column will be assigned a value.
The updated dataframe will look like this:
Output
A B D C
0 15 17 19 12
1 16 18 20 15
2 20 21 22 27
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