# 4. Getting Started¶

In this section we will take a high-level look at the basic things you can do with bitmath. We’ll include the following topics:

## 4.1. Tables of Supported Operations¶

The following legend describes the two operands used in the tables below.

Operand Description
bm A bitmath object is required
num An integer or decimal value is required

### 4.1.1. Arithmetic¶

Math works mostly like you expect it to, except for a few edge-cases:

• Mixing bitmath types with Number types (the result varies per-operation)
• Operations where two bitmath types would cancel out (such as dividing two bitmath types)
• Multiplying two bitmath instances together is supported, but the results may not make much sense.

Appendix: Rules for Math
For a discussion of the behavior of bitmath and number types.
Operation Parameters Result Type Example
Addition bm1 + bm2 type(bm1) KiB(1) + MiB(2) = 2049.0KiB
Addition bm + num type(num) KiB(1) + 1 = 2.0
Addition num + bm type(num) 1 + KiB(1) = 2.0
Subtraction bm1 - bm2 type(bm1) KiB(1) - Byte(2048) = -1.0KiB
Subtraction bm - num type(num) KiB(4) - 1 = 3.0
Subtraction num - bm type(num) 10 - KiB(1) = 9.0
Multiplication bm1 * bm2 type(bm1) KiB(1) * KiB(2) = 2048.0KiB
Multiplication bm * num type(bm) KiB(2) * 3 = 6.0KiB
Multiplication num * bm type(bm) 2 * KiB(3) = 6.0KiB
Division bm1 / bm2 type(num) KiB(1) / KiB(2) = 0.5
Division bm / num type(bm) KiB(1) / 3 = 0.3330078125KiB
Division num / bm type(num) 3 / KiB(2) = 1.5

### 4.1.2. Bitwise Operations¶

Bitwise Calculator
A free online calculator for checking your math

Bitwise operations are also supported. Bitwise operations work directly on the bits attribute of a bitmath instance, not the number you see in an instances printed representation (value), to maintain accuracy.

Operation Parameters Result Type Example1
Left Shift bm << num type(bm) MiB(1) << 2 = MiB(4.0)
Right Shift bm >> num type(bm) MiB(1) >> 2 = MiB(0.25)
AND bm & num type(bm) MiB(13.37) & 1337 = MiB(0.000126...)
OR bm | num type(bm) MiB(13.37) | 1337 = MiB(13.3700...)
XOR bm ^ num type(bm) MiB(13.37) ^ 1337 = MiB(13.369...)
1. Give me a break here, it’s not easy coming up with compelling examples for bitwise operations...

## 4.2. Basic Math¶

bitmath supports all arithmetic operations

 1 2 3 4 5 6 7 8 9 In [7]: eighty_four_mib = fourty_two_mib + fourty_two_mib_in_kib In [8]: eighty_four_mib Out[8]: MiB(84.0) In [9]: eighty_four_mib == fourty_two_mib * 2 Out[9]: True 

## 4.3. Unit Conversion¶

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 In [1]: from bitmath import * In [2]: fourty_two_mib = MiB(42) In [3]: fourty_two_mib_in_kib = fourty_two_mib.to_KiB() In [4]: fourty_two_mib_in_kib Out[4]: KiB(43008.0) In [5]: fourty_two_mib Out[5]: MiB(42.0) In [6]: fourty_two_mib.KiB Out[6]: KiB(43008.0) 

## 4.4. Rich Comparison¶

Rich Comparison (as per the Python Basic Customization magic methods): <, <=, ==, !=, >, >= is fully supported:

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 In [2]: GB(1) < GiB(1) Out[2]: True In [3]: GB(1.073741824) == GiB(1) Out[3]: True In [4]: GB(1.073741824) <= GiB(1) Out[4]: True In [5]: Bit(1) == TiB(bits=1) Out[5]: True In [6]: kB(100) > EiB(bytes=1024) Out[6]: True In [7]: kB(100) >= EiB.from_other(kB(100)) Out[7]: True In [8]: kB(100) >= EiB.from_other(kB(99)) Out[8]: True In [9]: kB(100) >= EiB.from_other(kB(9999)) Out[9]: False In [10]: KiB(100) != Byte(1) Out[10]: True 

## 4.5. Sorting¶

bitmath natively supports sorting.

Let’s make a list of the size (in bytes) of all the files in the present working directory (lines 7 and 8) and then print them out sorted by increasing magnitude (lines 13 and 14, and 18 and 19):

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 In [1]: from bitmath import * In [2]: import os In [3]: sizes = [] In [4]: for f in os.listdir('./tests/'): sizes.append(KiB(os.path.getsize('./tests/' + f))) In [5]: print sizes [KiB(7337.0), KiB(1441.0), KiB(2126.0), KiB(2178.0), KiB(2326.0), KiB(4003.0), KiB(48.0), KiB(1770.0), KiB(7892.0), KiB(4190.0)] In [6]: print sorted(sizes) [KiB(48.0), KiB(1441.0), KiB(1770.0), KiB(2126.0), KiB(2178.0), KiB(2326.0), KiB(4003.0), KiB(4190.0), KiB(7337.0), KiB(7892.0)] In [7]: human_sizes = [s.best_prefix() for s in sizes] In [8]: print sorted(human_sizes) [KiB(48.0), MiB(1.4072265625), MiB(1.728515625), MiB(2.076171875), MiB(2.126953125), MiB(2.271484375), MiB(3.9091796875), MiB(4.091796875), MiB(7.1650390625), MiB(7.70703125)] 

Now print them out in descending magnitude

In [8]: print sorted(human_sizes, reverse=True)
[KiB(7892.0), KiB(7337.0), KiB(4190.0), KiB(4003.0), KiB(2326.0), KiB(2178.0), KiB(2126.0), KiB(1770.0), KiB(1441.0), KiB(48.0)]