'''
01 - Bar chart

Bar charts visualize data that is organized according to categories  as  a  series  of 
bars, where the height of each bar represents the values of the data in this category.

For example, in this exercise,  you will  visualize the  number  of  gold  medals  won  by  each 
country in the provided medals  DataFrame. The DataFrame contains the  countries  as  the  index, 
and a column called "Gold" that contains the number of gold medals won by each country, according 
to their rows.

Instructions:

- Call the ax.bar method to plot the "Gold" column as a function of the country.
- Use the ax.set_xticklabels to set the x-axis tick labels to be the country names.
- In the call to ax.set_xticklabels rotate the x-axis tick labels by 90 degrees by using the rotation
  key-word argument.
- Set the y-axis label to "Number of medals".
'''

fig, ax = plt.subplots()

# Plot a bar-chart of gold medals as a function of country
ax.bar(medals.index, medals['Gold'])

# Set the x-axis tick labels to the country names
ax.set_xticklabels(medals.index, rotation=90)

# Set the y-axis label
ax.set_ylabel('Number of medals')

plt.show()