# Create the series of countries: countries
countries = gapminder_melt.country

# Drop all the duplicates from countries
countries = countries.drop_duplicates()

# Write the regular expression: pattern
pattern = '^[A-Za-z\.\s]*$'

# Create the Boolean vector: mask
mask = countries.str.contains(pattern)

# Invert the mask: mask_inverse
mask_inverse = ~mask

# Subset countries using mask_inverse: invalid_countries
invalid_countries = countries.loc[mask_inverse]

# Print invalid_countries
print(invalid_countries)

b0a4c347201767fd95e8f53355bae7065bd69911
<mask token>

<mask token>
print(invalid_countries)

countries = gapminder_melt.country
countries = countries.drop_duplicates()
pattern = '^[A-Za-z\\.\\s]*$'
mask = countries.str.contains(pattern)
mask_inverse = ~mask
invalid_countries = countries.loc[mask_inverse]
print(invalid_countries)

# Create the series of countries: countries
countries = gapminder_melt.country

# Drop all the duplicates from countries
countries = countries.drop_duplicates()

# Write the regular expression: pattern
pattern = '^[A-Za-z\.\s]*$'

# Create the Boolean vector: mask
mask = countries.str.contains(pattern)

# Invert the mask: mask_inverse
mask_inverse = ~mask

# Subset countries using mask_inverse: invalid_countries
invalid_countries = countries.loc[mask_inverse]

# Print invalid_countries
print(invalid_countries)
