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author | Matti Picus <matti.picus@gmail.com> | 2020-09-02 21:01:35 +0300 |
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committer | GitHub <noreply@github.com> | 2020-09-02 13:01:35 -0500 |
commit | 1f8ce6341159ebb0731c2c262f4576609210d2c8 (patch) | |
tree | aa10443358243366d776ad669c0cbcd383ed3634 /numpy/doc/misc.py | |
parent | e3c84a44b68966ab887a3623a0ff57169e508deb (diff) | |
download | numpy-1f8ce6341159ebb0731c2c262f4576609210d2c8.tar.gz |
MAINT, DOC: move informational files from numpy.doc.*.py to their *.rst counterparts (#17222)
* DOC: redistribute docstring-only content from numpy/doc
* DOC: post-transition clean-up
* DOC, MAINT: reskip doctests, fix a few easy ones
Diffstat (limited to 'numpy/doc/misc.py')
-rw-r--r-- | numpy/doc/misc.py | 226 |
1 files changed, 0 insertions, 226 deletions
diff --git a/numpy/doc/misc.py b/numpy/doc/misc.py deleted file mode 100644 index fc1c4cd01..000000000 --- a/numpy/doc/misc.py +++ /dev/null @@ -1,226 +0,0 @@ -""" -============= -Miscellaneous -============= - -IEEE 754 Floating Point Special Values --------------------------------------- - -Special values defined in numpy: nan, inf, - -NaNs can be used as a poor-man's mask (if you don't care what the -original value was) - -Note: cannot use equality to test NaNs. E.g.: :: - - >>> myarr = np.array([1., 0., np.nan, 3.]) - >>> np.nonzero(myarr == np.nan) - (array([], dtype=int64),) - >>> np.nan == np.nan # is always False! Use special numpy functions instead. - False - >>> myarr[myarr == np.nan] = 0. # doesn't work - >>> myarr - array([ 1., 0., NaN, 3.]) - >>> myarr[np.isnan(myarr)] = 0. # use this instead find - >>> myarr - array([ 1., 0., 0., 3.]) - -Other related special value functions: :: - - isinf(): True if value is inf - isfinite(): True if not nan or inf - nan_to_num(): Map nan to 0, inf to max float, -inf to min float - -The following corresponds to the usual functions except that nans are excluded -from the results: :: - - nansum() - nanmax() - nanmin() - nanargmax() - nanargmin() - - >>> x = np.arange(10.) - >>> x[3] = np.nan - >>> x.sum() - nan - >>> np.nansum(x) - 42.0 - -How numpy handles numerical exceptions --------------------------------------- - -The default is to ``'warn'`` for ``invalid``, ``divide``, and ``overflow`` -and ``'ignore'`` for ``underflow``. But this can be changed, and it can be -set individually for different kinds of exceptions. The different behaviors -are: - - - 'ignore' : Take no action when the exception occurs. - - 'warn' : Print a `RuntimeWarning` (via the Python `warnings` module). - - 'raise' : Raise a `FloatingPointError`. - - 'call' : Call a function specified using the `seterrcall` function. - - 'print' : Print a warning directly to ``stdout``. - - 'log' : Record error in a Log object specified by `seterrcall`. - -These behaviors can be set for all kinds of errors or specific ones: - - - all : apply to all numeric exceptions - - invalid : when NaNs are generated - - divide : divide by zero (for integers as well!) - - overflow : floating point overflows - - underflow : floating point underflows - -Note that integer divide-by-zero is handled by the same machinery. -These behaviors are set on a per-thread basis. - -Examples --------- - -:: - - >>> oldsettings = np.seterr(all='warn') - >>> np.zeros(5,dtype=np.float32)/0. - invalid value encountered in divide - >>> j = np.seterr(under='ignore') - >>> np.array([1.e-100])**10 - >>> j = np.seterr(invalid='raise') - >>> np.sqrt(np.array([-1.])) - FloatingPointError: invalid value encountered in sqrt - >>> def errorhandler(errstr, errflag): - ... print("saw stupid error!") - >>> np.seterrcall(errorhandler) - <function err_handler at 0x...> - >>> j = np.seterr(all='call') - >>> np.zeros(5, dtype=np.int32)/0 - FloatingPointError: invalid value encountered in divide - saw stupid error! - >>> j = np.seterr(**oldsettings) # restore previous - ... # error-handling settings - -Interfacing to C ----------------- -Only a survey of the choices. Little detail on how each works. - -1) Bare metal, wrap your own C-code manually. - - - Plusses: - - - Efficient - - No dependencies on other tools - - - Minuses: - - - Lots of learning overhead: - - - need to learn basics of Python C API - - need to learn basics of numpy C API - - need to learn how to handle reference counting and love it. - - - Reference counting often difficult to get right. - - - getting it wrong leads to memory leaks, and worse, segfaults - - - API will change for Python 3.0! - -2) Cython - - - Plusses: - - - avoid learning C API's - - no dealing with reference counting - - can code in pseudo python and generate C code - - can also interface to existing C code - - should shield you from changes to Python C api - - has become the de-facto standard within the scientific Python community - - fast indexing support for arrays - - - Minuses: - - - Can write code in non-standard form which may become obsolete - - Not as flexible as manual wrapping - -3) ctypes - - - Plusses: - - - part of Python standard library - - good for interfacing to existing sharable libraries, particularly - Windows DLLs - - avoids API/reference counting issues - - good numpy support: arrays have all these in their ctypes - attribute: :: - - a.ctypes.data a.ctypes.get_strides - a.ctypes.data_as a.ctypes.shape - a.ctypes.get_as_parameter a.ctypes.shape_as - a.ctypes.get_data a.ctypes.strides - a.ctypes.get_shape a.ctypes.strides_as - - - Minuses: - - - can't use for writing code to be turned into C extensions, only a wrapper - tool. - -4) SWIG (automatic wrapper generator) - - - Plusses: - - - around a long time - - multiple scripting language support - - C++ support - - Good for wrapping large (many functions) existing C libraries - - - Minuses: - - - generates lots of code between Python and the C code - - can cause performance problems that are nearly impossible to optimize - out - - interface files can be hard to write - - doesn't necessarily avoid reference counting issues or needing to know - API's - -5) scipy.weave - - - Plusses: - - - can turn many numpy expressions into C code - - dynamic compiling and loading of generated C code - - can embed pure C code in Python module and have weave extract, generate - interfaces and compile, etc. - - - Minuses: - - - Future very uncertain: it's the only part of Scipy not ported to Python 3 - and is effectively deprecated in favor of Cython. - -6) Psyco - - - Plusses: - - - Turns pure python into efficient machine code through jit-like - optimizations - - very fast when it optimizes well - - - Minuses: - - - Only on intel (windows?) - - Doesn't do much for numpy? - -Interfacing to Fortran: ------------------------ -The clear choice to wrap Fortran code is -`f2py <https://docs.scipy.org/doc/numpy/f2py/>`_. - -Pyfort is an older alternative, but not supported any longer. -Fwrap is a newer project that looked promising but isn't being developed any -longer. - -Interfacing to C++: -------------------- - 1) Cython - 2) CXX - 3) Boost.python - 4) SWIG - 5) SIP (used mainly in PyQT) - -""" |