Integer Objects

Working with Python int type (arbitrary precision integers)

Overview

Python integers (int) support arbitrary precision - they can represent integers of any size limited only by available memory.

Type Object

PyTypeObject PyLong_Type

The Python int type.

Type Checking

int PyLong_Check(PyObject *p)
int PyLong_CheckExact(PyObject *p)

Check if object is an integer or exactly an integer (not subclass).

Creating Integers

From C Types

PyObject* PyLong_FromLong(long v)
PyObject* PyLong_FromUnsignedLong(unsigned long v)
PyObject* PyLong_FromLongLong(long long v)
PyObject* PyLong_FromUnsignedLongLong(unsigned long long v)
PyObject* PyLong_FromSize_t(size_t v)
PyObject* PyLong_FromSsize_t(Py_ssize_t v)
PyObject* PyLong_FromDouble(double v)

Example:

PyObject *num = PyLong_FromLong(42);
if (num == NULL)
    return PyErr_NoMemory();
return num;

From Strings

PyObject* PyLong_FromString(const char *str, char **pend, int base)

Parse integer from string with specified base (2-36, or 0 for auto-detect).

Example:

PyObject *num = PyLong_FromString("ff", NULL, 16);  // Returns 255

Converting to C Types

long PyLong_AsLong(PyObject *obj)
unsigned long PyLong_AsUnsignedLong(PyObject *obj)
long long PyLong_AsLongLong(PyObject *obj)
unsigned long long PyLong_AsUnsignedLongLong(PyObject *obj)
Py_ssize_t PyLong_AsSsize_t(PyObject *obj)
double PyLong_AsDouble(PyObject *obj)

Returns: Converted value, or -1 on error (check PyErr_Occurred())

Example:

long value = PyLong_AsLong(obj);
if (value == -1 && PyErr_Occurred()) {
    // Handle overflow or type error
    return NULL;
}
printf("Value: %ld\\n", value);

With Overflow Detection

long PyLong_AsLongAndOverflow(PyObject *obj, int *overflow)

overflow · int*

Set to -1, 0, or 1 indicating underflow, success, or overflow

Example:

int overflow;
long value = PyLong_AsLongAndOverflow(obj, &overflow);

if (overflow != 0) {
    if (overflow < 0)
        printf("Value too small for long\\n");
    else
        printf("Value too large for long\\n");
    return NULL;
}

Complete Example

static PyObject* add_integers(PyObject *self, PyObject *args) {
    PyObject *a, *b;
    long val_a, val_b, result;
    
    if (!PyArg_ParseTuple(args, "OO", &a, &b))
        return NULL;
    
    // Check types
    if (!PyLong_Check(a) || !PyLong_Check(b)) {
        PyErr_SetString(PyExc_TypeError, "Arguments must be integers");
        return NULL;
    }
    
    // Convert to C long
    val_a = PyLong_AsLong(a);
    if (val_a == -1 && PyErr_Occurred())
        return NULL;
    
    val_b = PyLong_AsLong(b);
    if (val_b == -1 && PyErr_Occurred())
        return NULL;
    
    // Perform operation
    result = val_a + val_b;
    
    // Return as Python int
    return PyLong_FromLong(result);
}

See Also

• Boolean Objects - Booleans are a subclass of int
• Floating Point Objects
• Object Protocol