Python - 関数(キーワード引数)

開発環境

• OS X Lion - Apple(OS)
• TextWrangler(Text Editor) (BBEditの無料機能制限版、light版)
• Script言語: Python

『初めてのPython 第3版』(Mark Lutz 著、夏目 大 訳、オライリー・ジャパン、2009年、ISBN978-4-87311-393-7) のIV部(関数)まとめ演習4(キーワード引数)を解いてみる。

4.

コード(TextWrangler)

#!/usr/bin/env python
#encoding: utf-8

def adder(good=10,bad=20,ugly=30):
 return good + bad + ugly

入出力結果(Terminal)

$ python
Python 2.7.2 (default, Feb 12 2012, 23:50:38) 
[GCC 4.2.1 Compatible Apple Clang 3.0 (tags/Apple/clang-211.12)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from python_program import adder
>>> print adder(5)
55
>>> print adder(5,6)
41
>>> print adder(5,6,7)
18
>>> print adder(5,6,7,8)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: adder() takes at most 3 arguments (4 given)
>>> print adder('a')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "python_program.py", line 5, in adder
    return good + bad + ugly
TypeError: cannot concatenate 'str' and 'int' objects
>>> 'a'+1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot concatenate 'str' and 'int' objects
>>> 1+'a'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'
>>> print adder(ugly=1,good=2)
23
>>> quit()
$

adder関数をさらに改良

コード(TextWrangler)

#!/usr/bin/env python
#encoding: utf-8

def adder(**args):
 L = []
 for key in args.keys():
  L.append(args[key])
 result = L[0]
 for x in L[1:]:
  result += x
 return result

print adder(a=1,b=2,c=3,d=4,e=5)

入出力結果(Terminal)

$ python python_program.py
15
$