list, dictionary comprehensionのサンプル

dictionary-comprehension.py

"""
dictionary-comprehension
"""

# Pythonはdictionary comprehensionもサポートしている
# syntax: <variable> = { key:new_value for (key, value) in <dictionary>.items() }
grades = {'Nora': 90, 'Lulu': 15, 'Gino': 60}
grades
# ---> {'Nora': 90, 'Lulu': 15, 'Gino': 60}

doubleGrades = { key: value*2 for (key, value) in grades.items() }
doubleGrades
# ---> {'Nora': 180, 'Lulu': 30, 'Gino': 120}

# もちろん、<condition>も追加することもできる
doubleGrades = { key: value*2 for (key, value) in grades.items() if value % 2 ==0 }
doubleGrades

list-comprehension.py

"""
list-comprehension
"""

# Without list comprehension
list1 = []
for i in range(15):
    if i % 2 ==0:
        list1.append(i)
list1
# ---> [0, 2, 4, 6, 8, 10, 12, 14]

# With list comprehensions
# syntax: [<value_to_include> for <elem> in <sequence> if <condition>]
list2 = [i for i in range(15) if i % 2 == 0]
list2
# ---> [0, 2, 4, 6, 8, 10, 12, 14]

# <condition>はoptional
list3 = [i for i in range(15)]
list3
# ---> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]