Practice HW9: List Comprehensions

In this practice HW you will explore writing some list comprehensions.

Rx: <5 min Av: 5-10 min Sd: 10-15 min DNF: 15+ min

Write python code (as a program or in the python interpreter) that prints out the following using list comprehensions of the form:

print([c for x in sequence])

where c is the computation and x is an element in a sequence. Remember that you can also put an if after the sequence to further restrict what elements are added to the list.

You should be able to print:

• twelve 12’s
• the absolute values from -10 to 10
• the even numbers from 0 to 100
• the perfect squares from 0 to 100
• the number of odd numbers in the range of 0 to 100
• the number of consonants in the string “Hi there”
• the string “CS rocks!” with no vowels

Solution

When you’ve attempted the PHW, you can see my solution below. Scroll down!

>>> print([12 for x in range(12)])
[12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12]

>>> print([abs(x) for x in range(-10,11)])
[10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

>>> print([x for x in range(101) if x % 2 == 0])
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100]

>>> print([x**2 for x in range(1, 101) if x**2 < 100])
[1, 4, 9, 16, 25, 36, 49, 64, 81]

>>> print(sum([1 for x in range(101) if x % 2 == 1]))
50

>>> print(sum([1 for x in "Hello, there!" if x in "AEIOUaeiou"]))
4

>>> print( “”.join( [ x for x in “CS rocks!” if x not in "AEIOUaeiou" ] ) )
"CS rcks!"