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Bit flags implementation using a C Union. This library removes the need to use ctypes and helps you quickly access what bits are toggled.

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Bit flags implementation using a C Union. This library removes the need to use ctypes and helps you quickly access what bits are toggled.

This class is built off of the Bit Manipulation guide found at https://wiki.python.org/moin/BitManipulation under the Bit fields section.

This library includes a class based approach to bit flags (BitFlags) and a one time dynamic bit flags object (bitflags).

The individual bits can always be accessed with ‘flag.bit_0’, ‘flag.bit_1’, ‘flag.bit_2’, …

Example - BitFlags

This is the class based approach.

from bitflags import BitFlags


class MyFlags(BitFlags):
    options = {0: "flag1", 1: "flag2", 2: "flag3", 3: "flag4", 4: "Something Happened"}


f = MyFlags(0)

assert f.value == 0
assert int(f) == 0

f.value = 0b101  # 5 - bin(5) shows the bit values (0b101)
assert f.value == 0b101

# You can always access the bit value with 'bit_X'
# Access all of the bits (The number of bits can be changed by setting the class attribute nbits or nbytes
print(f.bit_7, f.bit_6, f.bit_5, f.bit_4, f.bit_3, f.bit_2, f.bit_1, f.bit_0)
# 0 0 0 0 0 1 0 1

# Access the custom flags as attributes
assert f.flag1 == 1
assert f.flag2 == 0
assert f.flag3 == 1
assert f.flag4 == 0
assert f.something_happened == 0

# Get a list of flag options
assert f.get_flags() == ['flag1', 'flag3']

# Convert to use the data types
assert str(f) == 'flag1, flag3'
assert int(f) == 5
assert bytes(f) == b'\x05'

This class was made to be flexible if you want the attributes to be different from the display options.

from bitflags import BitFlags


class MyFlags(BitFlags):
    options = {0: "Failure", 1: "Warning", 2: "System 2% Overloaded"}

f = MyFlags(0b111)
assert hasattr(f, 'failure')
assert hasattr(f, 'warning')
assert hasattr(f, 'system_2_overloaded')

assert f.get_flags() == ['Failure', 'Warning', 'System 2% Overloaded']


class SpecialFlags(BitFlags):
    options = {0: "2% System Failure",  # Note: variable name cannot start with a number!
               1: "System Overloaded",
               2: "System Safe"}
    fields = {'system_failure': 0, 'system_overload': 1, 'safe': 2}  # Custom variables to access the bits

s = SpecialFlags(7)

assert s.system_failure == 1
assert s.system_overload == 1
assert s.safe == 1

assert s.get_flags() == ["2% System Failure", "System Overloaded", "System Safe"]


s2 = SpecialFlags(1)
assert s.get_flags() == ["2% System Failure"]

You can also make a pattern for options.

from bitflags import BitFlags


class MyFlags(BitFlags):
    pattern = '%i'

f = MyFlags()
f.value = 0b101  # 5 - bin(5) shows the bit values (0b101)
assert f.value == 0b101

# Get a list of flag options
assert f.get_flags() == ['0', '2']

# Convert to use the data types
assert str(f) == '0, 2'
assert int(f) == 5
assert bytes(f) == b'\x05'

Example - bitflags

The one time object bit flags. This is basically the same thing as BitFlags only the instance constructor allows you to set the options, fields, and number of bits/bytes.

from bitflags import bitflags

f = bitflags(flag1=1, flag3=1, options={0: "flag1", 1: "flag2", 2: "flag3", 3: "flag4", 4: "Something Happened"})

assert f.value == 0b101

assert f.flag1 == 1
assert f.flag2 == 0
assert f.flag3 == 1
assert f.flag4 == 0
assert f.something_happened == 0

# Change the fields that access the bits.
f.set_fields({'a': 0, 'b': 1, 'c': 2, 'd': 3})

assert f.a == f.bit_0
assert f.b == f.bit_1
assert f.c == f.bit_2
assert f.d == f.bit_3

The bitflags constructor uses type to create a new BitFlags class. This class isn’t really re-usable unless you access that class from the object that was created.

from bitflags import bitflags

f = bitflags(flag1=1, flag3=1, options={0: "flag1", 1: "flag2", 2: "flag3", 3: "flag4", 4: "Something Happened"})

assert f.value == 0b101

f2 = type(f)(0b1)
assert f2.flag1 == 1
assert f2.value == 1
assert f.value == 0b101

f3 = f.__class__(0b10)
assert f3.flag1 == 0
assert f3.flag2 == 1
assert f3.value == 2
assert f2.value == 1
assert f.value == 0b101

If you want to use multiple bit flag objects that have the same fields then it is better to use BitFlags class inheritance.

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