простой код:
i = 0
while i < 5:
i += 0.1
print("i = ", i)
результат:
i = 0.1
i = 0.2
i = 0.30000000000000004
i = 0.4
i = 0.5
i = 0.6
i = 0.7
i = 0.7999999999999999
i = 0.8999999999999999
i = 0.9999999999999999
i = 1.0999999999999999
i = 1.2
i = 1.3
i = 1.4000000000000001
Откуда берется погрешность?