Caveats

Since Cython mixes C and Python semantics, some things may be a bitsurprising or unintuitive. Work always goes on to make Cython more naturalfor Python users, so this list may change in the future.

• Given two typed int variables a and b, a % b has the
  same sign as the second argument (following Python semantics) rather than
  having the same sign as the first (as in C). The C behavior can be
  obtained, at some speed gain, by enabling the cdivision directive
  (versions prior to Cython 0.12 always followed C semantics).


• Care is needed with unsigned types. cdef unsigned n = 10;
print(range(-n, n)) will print an empty list, since -n wraps
  around to a large positive integer prior to being passed to the
  range function.


• Python’s float type actually wraps C double values, and
  the int type in Python 2.x wraps C long values.