September 2014
Intermediate to advanced
332 pages
6h 48m
Japanese
Content preview from Python文法詳解
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284
第 7 章 データ型とプロトコル
class MutableSpam:
val = 1
def __iadd__(self, other):
#
自分自身を更新する場合、
self
を戻り値とする
self.val += other
return self
class ImmutableSpam:
val = 1
def __iadd__(self, other):
#
新しいオブジェクトを代入する場合は、そのオブジェクトを戻り値とする
ret = Spam()
ret.val = self.val * other
return ret
7.8.5
数値変換
表
7-9
数値変換
式 メソッド
bool(obj) __bool__(self)
complex(obj) __complex__(self)
int(obj) __int__(self)
float(obj) __float___(self)
__int__()
などの数値変換メソッドは、
int()
などから呼び出され、それぞれのデータ型に変
換した値を返します。
数値変換メソッドは、演算中に発生する暗黙の型変換でも呼び出され、
10 + obj
という式は、
10 + obj.__int__()
のように、オブジェクトの
__int__()
メソッドを呼び出し、値を整数値に変換して、演算を行
います。
__bool__()
メソッドは、オブジェクトを
bool
型に変換する時に呼び出され、
True
また
は
False
を返します。
if
文などで値の真偽を判定するときにも、
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