Numeric
- Constants
- Create
- Test
- Convert
Constants
| What | How | Details |
| NaN | math.nan | |
| NaN | float('nan') | |
| NaN | numpy.nan | |
| Infinity | math.inf | |
| Infinity | float('inf') | |
| Infinity | numpy.inf | |
| Negative infinity | -math.inf | |
| Negative infinity | float('-inf') | |
| Negative infinity | numpy.NINF | |
| Pi | math.pi | |
| e | math.e | |
| Min int | -sys.maxsize | |
| Max int | sys.maxsize | |
| Float epsilon (smallest representable difference) | sys.float_info.epsilon | |
| Min float | sys.float_info.min | |
| Max float | sys.float_info.max | |
Create
int() and float() throw ValueError if the input cannot be parsed.
| What | How | Details |
| Binary integer | [sign]0b[b2int] | e.g., -0b10 (-2) |
| Hex integer | [sign]0x[b16int] | e.g., -0xF (-16) |
| Integer from string | int(x) | |
| Integer from hex string (base 16) | int(x, 16) | e.g., DEADBEEF |
| Integer from string with base determined by prefix | int(x, 0) | Base 10 by default, base-16 for 0x, base-2 for 0b |
| Integer from string according to locale | locale.atoi(x) | |
| Unsigned integer from bytes | int.from_bytes(x, byteorder='big') | |
| Signed integer from bytes | int.from_bytes(x, byteorder='big', signed=True) | |
| Float from string | float(x) | Throws ValueError if string cannot be parsed |
Float from packed struct bytes | struct.unpack('f', x)[0] | e.g., b'\x00\x00 @' |
| Float from hex string representation | float.fromhex(x) | |
| Float from string for locale | locale.atof(x) | |
| Float from string for temporary locale | Babel.parse_decimal('1,25', locale='nl_NL.utf8') | No way to do this cleanly and thread-safe in standard Python… |
| Float from string for temporary locale | loc = locale.getlocale(locale.LC_NUMERIC)
locale.setlocale(locale.LC_NUMERIC, 'nl_NL')
f = locale.atof(x)
locale.setlocale(locale.LC_NUMERIC, loc) | |
| What | How | Details |
| Number of bits needed to represent the integer (ignoring sign) | x.bit_length() | Same as floor(log2(|x|)) |
Test
| What | How | Details |
| Integer | | |
| Whole number | float.is_integer(x) | e.g., TRUE for 5.0 |
| Approximately equal | math.isclose(x, y) | Uses proportional tolerance |
| Approximately equal with absolute tolerance tol | math.isclose(x, y, abs_tol=tol) | |
| Approximately equal with proportional tolerance tol% | math.isclose(x, y, rel_tol=tol) | |
| NaN | math.isnan(x) | Does not work for complex numbers |
| Finite | math.isfinite(x) | |
| Infinite | math.isinf(x) | |
| Positive infinity | math.isinf(x) and x > 0 | |
| Negative infinity | math.isinf(x) and x < 0 | |
Convert
| What | How | Details |
| String | str(x) | |
| Float to string according to locale | locale.str(float) | |
| Hash | hash(x) | |
| Count to bytes | x.to_bytes(8, byteorder='big') | OverflowError is raised if the integer is not representable with the given number of bytes |
| Count to byte array (mutable) | bytearray(x) | |
| Integer to bytes | x.to_bytes(8, byteorder='big', signed=True) | |
| Float to bytes | struct.pack('f', x) | |
| Int to hex string | hex(x) | Format: [sign] ['0x'] integer |
| Float to hex string representation | x.hex() | Format: [sign] ['0x'] integer ['.' fraction] ['p' exponent], e.g., 0x1.400000p+1 |