Python での高度なプログラミングに関するいくつかのヒントのまとめ

num = [1, 4, -5, 10, -7, 2, 3, -1]
filtered_and_squared = []
 
for number in num:
 if number > 0:
 filtered_and_squared.append(number ** 2)
print filtered_and_squared
 
# [1, 16, 100, 4, 9]

num = [1, 4, -5, 10, -7, 2, 3, -1]
filtered_and_squared = map(lambda x: x ** 2, filter(lambda x: x > 0, num))
print filtered_and_squared
 
# [1, 16, 100, 4, 9]

num = [1, 4, -5, 10, -7, 2, 3, -1]
filtered_and_squared = [ x**2 for x in num if x > 0]
print filtered_and_squared
 
# [1, 16, 100, 4, 9]

num = [1, 4, -5, 10, -7, 2, 3, -1]
filtered_and_squared = ( x**2 for x in num if x > 0 )
print filtered_and_squared
 
# <generator object <genexpr> at 0x00583E18>
 
for item in filtered_and_squared:
 print item
 
# 1, 16, 100 4,9

num = [1, 4, -5, 10, -7, 2, 3, -1]
 
def square_generator(optional_parameter):
 return (x ** 2 for x in num if x > optional_parameter)
 
print square_generator(0)
# <generator object <genexpr> at 0x004E6418>
 
# Option I
for k in square_generator(0):
 print k
# 1, 16, 100, 4, 9
 
# Option II
g = list(square_generator(0))
print g
# [1, 16, 100, 4, 9]

alist = ['a1', 'a2', 'a3']
blist = ['1', '2', '3']
 
for a, b in zip(alist, blist):
 print a, b
 
# a1 1
# a2 2
# a3 3

import os
def tree(top):
 for path, names, fnames in os.walk(top):
 for fname in fnames:
  yield os.path.join(path, fname)
 
for name in tree('C:\Users\XXX\Downloads\Test'):
 print name

import time
from functools import wraps
 
def timethis(func):
 '''
 Decorator that reports the execution time.
 '''
 @wraps(func)
 def wrapper(*args, **kwargs):
 start = time.time()
 result = func(*args, **kwargs)
 end = time.time()
 print(func.name, end-start)
 return result
 return wrapper
 
@timethis
def countdown(n):
 while n > 0:
 n -= 1
 
countdown(100000)
 
# ('countdown', 0.006999969482421875)

@timethis
def countdown(n):

def countdown(n):
...
countdown = timethis(countdown)

@decorator
def function():
 print("inside function")

class decorator(object):
 
 def init(self, f):
 print("inside decorator.init()")
 f() # Prove that function definition has completed
 
 def call(self):
 print("inside decorator.call()")
 
@decorator
def function():
 print("inside function()")
 
print("Finished decorating function()")
 
function()
 
# inside decorator.init()
# inside function()
# Finished decorating function()
# inside decorator.call()