DataFrame applymap()

Question:

Start Quiz:

import pandas as pd

# Change False to True for this block of code to see what it does

# DataFrame applymap()
if False:
    df = pd.DataFrame({
        'a': [1, 2, 3],
        'b': [10, 20, 30],
        'c': [5, 10, 15]
    })
    
    def add_one(x):
        return x + 1
        
    print df.applymap(add_one)
    
grades_df = pd.DataFrame(
    data={'exam1': [43, 81, 78, 75, 89, 70, 91, 65, 98, 87],
          'exam2': [24, 63, 56, 56, 67, 51, 79, 46, 72, 60]},
    index=['Andre', 'Barry', 'Chris', 'Dan', 'Emilio', 
           'Fred', 'Greta', 'Humbert', 'Ivan', 'James']
)
    
def convert_grades(grades):
    '''
    Fill in this function to convert the given DataFrame of numerical
    grades to letter grades. Return a new DataFrame with the converted
    grade.
    
    The conversion rule is:
        90-100 -> A
        80-89  -> B
        70-79  -> C
        60-69  -> D
        0-59   -> F
    '''
    return None

Solution:

INSTRUCTOR NOTE:

Note: The grader will execute your finished convert_grades(grades) function on some test grades DataFrames when you submit your answer. Make sure that this function returns a DataFrame with the converted grades.
Hint: You may need to define a helper function to use with .applymap().