如何在python大数计算中抑制科学记数法

Question

In python, when a large number(integer or float) is calculated, it seems that the number will be store in scientific notation and therefore become inaccurate. eg

>>> rst = 15
>>> dst = [10, 14, 10, 14, 10, 14, 10, 14, 10, 14, 10, 14, 10, 14]
>>> [float(dst[i])*float(rst)**float(i) for i in range(len(dst))]

[10.0, 210.0, 2250.0, 47250.0, 506250.0, 10631250.0, 113906250.0, 2392031250.0, 25628906250.0, 538207031250.0, 5766503906250.0, 121096582031250.0, 1297463378906250.0, 2.724673095703125e+16]
>>> # please note the last element is stored in scientific notation
>>> # but if calculate 14*15**13 (same as how the last element is calculated)
>>> 14*15**13
>>> 27246730957031250
>>> # result is fine
>>> 14*15**13 == dst[-1]
>>> False

how should I suppress scientific notation in python large number calculation

Answer 1

please note the last element is stored in scientific notation
but if calculate 14*15**13 (same as how the last element is calculated)

Last element is float , whilst result of 14**15**13 is int . If you are working solely with int s (and do not divide) you will get int in which case no e -notation is used.

Answer 2

Please note the difference between how a number is stored in memory and being used in calculations (as a float or int) and how it is converted to string and displayed on the screen (rounded as integer, fixed point or scientific notation). These are two completely independent concepts, so seeing something displayed in a certain way does not automatically say something about accuracy.

In [8]: i = 123

In [9]: print('integer displayed as int: %i, as fixed point: %.1f or %.3f, and in scientific notation: %e' % (i, i, i, i))
integer displayed as int: 123, as fixed point: 123.0 or 123.000, and in scientific notation: 1.230000e+02

In [10]: f = 1.23

In [11]: print('floating point displayed as int: %i, as fixed point: %.1f or %.3f, and in scientific notation: %e' % (f, f, f, f))
floating point displayed as int: 1, as fixed point: 1.2 or 1.230, and in scientific notation: 1.230000e+00