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math.floor()と//演算子の違いというかなんというか
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from math import floor | |
N = 1000000000000000000 # 10**18 | |
# //演算子を使った場合、意図した値になる | |
a = N//3 | |
print(a) | |
# 333333333333333333 | |
# floor()を使った場合、意図しない値になる | |
b = floor(N/3) | |
print(b) | |
# 333333333333333312 | |
# N/3 の値を出力すると、有効数字16桁で表現される | |
c = N/3 | |
print(c) | |
# 3.333333333333333e+17 | |
# cを f-strings で出力すると、誤差が生じる | |
print(f"{c:.10f}") | |
# 333333333333333312.0000000000 | |
# aも f-strings でfloat型に変換するように出力すると、誤差が生じるので注意 | |
print(f"{a:.10f}") | |
# 333333333333333312.0000000000 | |
# aは f-strings でfloat型に変換しなければ、誤差は生じない | |
print(f"{a:d}") | |
# 333333333333333333 |
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