Pandas Practice: Simple Query #2

Data Wrangling

Difficulty: 2 | Problem written by peter.washington

Educational Resource: https://web.stanford.edu/class/cs102/readings/pandasreferences.htm

Problem reported in interviews at


Pandas data manipulation is a crucial skill for a data scientist.For this problem, you are given as input a dataframe. Return a list of strings representing the elements of column b for which column a is a positive number.

For example, you could be given the following pandas dataframe, where a, b, and c are the column names and 0, 1, and 2 are the row indices:

   a b c

0 -1 2 3

1 400 5 6

2 700 8 9

In this case, you would return the following list of strings:

["5", "8"]

You can assume that there will always be at least 1 row where column a is positive.

Sample Input:
<class 'str'>
df: a b c 0 -100 2 3 1 400 5 6 2 700 8 9

Expected Output:
<class 'pandas.core.frame.DataFrame'>
0 0 5 1 8

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numpy has been already imported as np (import numpy as np)