12.5. Math Precision¶
12.5.1. float min and max¶
12.5.1.1. Maximal and minimal float values¶
import sys
sys.float_info.min # 2.2250738585072014e-308
sys.float_info.max # 1.7976931348623157e+308
12.5.1.2. Infinity representation¶
1e308 # 1e+308
1e309 # inf
float('inf') # inf
float('Infinity') # inf
float('-inf') # -inf
float('-Infinity') # -inf
12.5.1.3. Not-a-Number¶
float('nan')
# nan
float('-nan')
# nan
12.5.1.4. NaN vs Inf¶
float('inf') + float('inf') # inf
float('inf') + float('-inf') # nan
float('-inf') + float('inf') # nan
float('-inf') + float('-inf') # -inf
float('inf') - float('inf') # nan
float('inf') - float('-inf') # inf
float('-inf') - float('inf') # -inf
float('-inf') - float('-inf') # nan
float('inf') * float('inf') # inf
float('inf') * float('-inf') # -inf
float('-inf') * float('inf') # -inf
float('-inf') * float('-inf') # inf
float('inf') / float('inf') # nan
float('inf') / float('-inf') # nan
float('-inf') / float('inf') # nan
float('-inf') / float('-inf') # nan
12.5.2. Precision¶
12.5.3. doctests¶
def add_numbers(a, b):
"""
>>> add_numbers(2.5, 1.2)
3.7
>>> add_numbers(0.1, 0.2)
0.30000000000000004
>>> add_numbers(0.1, 0.2) # doctest: +ELLIPSIS
0.1 + 0.2 == 0.3000...
"""
return a + b
12.5.4. decimal¶
from decimal import Decimal
a = Decimal('0.1')
b = Decimal('0.2')
a + b
# Decimal('0.3')
from decimal import Decimal
a = Decimal('0.3')
float(a)
# 0.3