Add __enter__ and __exit__ methods

Author: dpryan79

py2bit.c

@@ -31,6 +31,19 @@ static PyObject *py2bitOpen(PyObject *self, PyObject *args, PyObject *kwds) {
     return NULL;
 }
 
+PyObject *py2bitEnter(pyTwoBit_t *self, PyObject *args) {
+    pyTwoBit_t *pytb = self->tb;
+
+    if(!pytb) {
+        PyErr_SetString(PyExc_RuntimeError, "The 2bit file handle is not opened!");
+        return NULL;
+    }
+
+    Py_INCREF(self);
+
+    return (PyObject*) self;
+}
+
 static void py2bitDealloc(pyTwoBit_t *self) {
     if(self->tb) twobitClose(self->tb);
     PyObject_DEL(self);

py2bit.h

@@ -10,6 +10,7 @@ typedef struct {
 } pyTwoBit_t;
 
 static PyObject* py2bitOpen(PyObject *self, PyObject *args, PyObject *kwds);
+static PyObject *py2bitEnter(pyTwoBit_t *pybw, PyObject *args);
 static PyObject *py2bitInfo(pyTwoBit_t *pybw, PyObject *args);
 static PyObject* py2bitClose(pyTwoBit_t *pybw, PyObject *args);
 static PyObject* py2bitChroms(pyTwoBit_t *pybw, PyObject *args);
@@ -145,6 +146,8 @@ bases. Counts may sum to less than the length of the region for the same reason.
 >>> tb.bases(tb, \"chr1\", 24, 74, True)\n\
 {'A': 6, 'C': 6, 'T': 6, 'G': 6}\n\
 >>> tb.close()"},
+    {"__enter__", (PyCFunction) py2bitEnter, METH_NOARGS, NULL},
+    {"__exit__", (PyCFunction) py2bitClose, METH_VARARGS, NULL},
     {NULL, NULL, 0, NULL}
 };