Styjun

first, I need to write a program that displays the names of the planets in the list Planets in descending order by their position from the Sun.
then, I should rite a program that displays the names of the planets in the list Planets in ascending order by the number of vowels in planet name.

I have been able to do the first part. however, I couldn't the second part.

Planets = [("Mercury", 75, 1), ("Venus", 460, 2), ("Mars", 140, 4),
 ("Earth", 510, 3), ("Jupiter", 62000, 5), ("Neptune", 7640, 8),
 ("Saturn", 42700, 6), ("Uranus", 8100, 7)]


def main():
 Planets.sort(key=Sort_By_Position,reverse=True)
 print("The names of the planets in descending order by their position from the Sun: ")
 for i in Planets:
 print (i[0])

 print(" ")

 print("Planets in ascending order by the number of vowels in planet name: ")
 Planets.sort(key=vowel_count)
 for i in Planets:
 print(i[0])

def Sort_By_Position(Planets):
 return Planets[-1]

def vowel_count():


main()

I expect the program to show me the ascending order of planets by the number of vowels in planet name.

here is solution

Planets = [("Mercury", 75, 1), ("Venus", 460, 2), ("Mars", 140, 4), ("Earth", 510, 3), ("Jupiter", 62000, 5), ("Neptune", 7640, 8), ("Saturn", 42700, 6), ("Uranus", 8100, 7)]

# decending order in order
new_pl=Planets.copy()
new_pl.sort(key=lambda x:x[2], reverse=True) # sorting on position value

print(new_pl)

"""
output
[('Neptune', 7640, 8), ('Uranus', 8100, 7), ('Saturn', 42700, 6), ('Jupiter', 62000, 5), ('Mars', 140, 4), ('Earth', 510, 3), ('Venus', 460, 2), ('Mercury', 75, 1)]
"""


# in no of vowels present
vowel = ['a','e','i','o','u']

# in vowels
def count(name):
 vowel = ['a','e','i','o','u']
 val=0
 for i in name.lower():
 if i in vowel:
 val+=1
 return val

new_pl_2=Planets.copy()

new_pl_2.sort(key=lambda x:count(x[0])) #sorting on count of vowels
print(new_pl_2)

"""
output

[('Mars', 140, 4), ('Mercury', 75, 1), ('Venus', 460, 2), ('Earth', 510, 3), ('Saturn', 42700, 6), ('Jupiter', 62000, 5), ('Neptune', 7640, 8), ('Uranus', 8100, 7)]
"""

You can do this in one line using a list comprehension.

def vowel_count(elem):
 return len([x for x in elem[0] if x in ('a', 'e', 'i', 'o', 'u')])

elem[0] contains the name of the planet you are iterating over. When you iterate over a string (x in elem[0]), it will iterate each individual character in that string. For example, 'Earth' becomes ['E', 'a', 'r', 't', 'h'].

From there, we can simply filter the list comprehension to only contain vowels (if x.lower() in ('a', 'e', 'i', 'o', 'u')) and return the length of the comprehension, which is fed back to the sort method.

You mentioned that you were able to do the first part so you are essentially only asking about the second part. The following example should help get you pointed in the right direction:

>>> planets = ['Mercury','Venus','Earth','Mars','Neptune','Jupiter','Saturn','Uranus']
>>> vowels = ('a','e','i','o','u')
>>> name_counts = []
>>> for name in planets:
... count = sum([1 for letter in name if letter.lower() in vowels])
... name_counts.append((name,count))
... 
>>> print(sorted(name_counts, key=lambda x: x[1]))
[('Mars', 1), ('Mercury', 2), ('Venus', 2), ('Earth', 2), ('Saturn', 2), ('Neptune', 3), ('Jupiter', 3), ('Uranus', 3)]