Metadata-Version: 1.0
Name: pyfil
Version: 0.7
Summary: Python one-liners in the shell in the spirit of Perl and AWK
Home-page: https://github.com/ninjaaron/pyfil
Author: Aaron Christianson
Author-email: ninjaaron@gmail.com
License: BSD
Description: pyfil
        =====
        Python one-liners in the spirit of Perl and AWK.
        
        ``pyfil`` gives you the ``rep`` command. This is because when I
        initially posted it in #python IRC channel, user [Tritium] (that ray of
        sunshine) said I had recreated the REP of the python REPL (read evaluate
        print loop). That is more or less the case. ``rep`` reads python
        expressions at the command line, evaluates them and prints them to
        stdout. It might be interesting as a quick calculator or to test
        something, like the Python REPL, but it also has some special flags for
        iterating on stdin and parsing JSON, which make it useful as a filter
        for shell one-liners or scripts (like Perl).
        
        pyfil is in pypi (i.e. you can get it easily with pip, if you want)
        
        note:
          pyfil has only been tested with python3, and only has wheels available
          for python3
        
        
        similar projects
        ~~~~~~~~~~~~~~~~
        pyfil ain't the first project to try something like this. Here are some
        other cracks at this problem:
        
        - oneliner_
        - pyp_
        - pyle_
        - funcpy_
        - red_
        
        .. _oneliner: http://python-oneliner.readthedocs.io/en/latest/
        .. _pyp: http://code.google.com/p/pyp
        .. _pyle: https://github.com/aljungberg/pyle
        .. _funcpy: http://www.pixelbeat.org/scripts/funcpy
        .. _red: https://bitbucket.org/johannestaas/red
        
        usage
        -----
        
        usage: rep [-h] [-l] [-q] [-j] [-b PRE] [-e POST] [-s] [-F PATTERN]
                   [-n STRING] [-R] [-S] [-H EXCEPTION_HANDLER]
                   expression [expression ...]
        
        positional arguments:
          expression            expression(s) to be executed.
        
        optional arguments:
          -h, --help            show this help message and exit
          -l, --loop            for i in sys.stdin: expression
          -q, --quiet           suppress automatic printing; If set, both statements
                                and expressions may be used
          -j, --json            load stdin as json into object 'j'; If used with
                                --loop, treat each line of stdin as a new object
          -b PRE, --pre PRE     expression to evaluate before the loop
          -e POST, --post POST  expression to evaluate after the loop
          -s, --split           split lines from stdin on whitespace into list 'f'.
                                implies --loop
          -F PATTERN, --field-sep PATTERN
                                regex used to split lines from stdin into list 'f'.
                                implies -l
          -n STRING, --join STRING
                                join items in iterables with STRING
          -R, --raise-errors    raise errors in evaluation and stop execution
                                (default: print message to stderr and continue)
          -S, --silence-errors  suppress error messages
          -H EXCEPTION_HANDLER, --exception-handler EXCEPTION_HANDLER
                                specify exception handler with the format ``Exception:
                                alternative expression to eval``
        
        
        available objects
        ~~~~~~~~~~~~~~~~~
        Automatically imports (unless overridden in ~/.config/pyfil-env.py):
        
        ``sys``, ``os``, ``re``, ``math``, ``pprint from pprint``, ``timeit
        from timeit`` and ``strftime from time``.
        
        If you'd like to specify a custom execution environment for rep, create
        ~/.config/pyfil-env.py and put things in it.
        
        The execution environment also has a special object for stdin,
        creatively named ``stdin``. This differs from sys.stdin in that it
        rstrips (aka chomps) all the lines when you iterate over it, and it has
        a property, ``stdin.l``, which returns a list of the (rstripped) lines.
        pyfil is quite bullish about using rstrip because python's print
        function will supply an additional newline, and if you just want the
        value of the text in the line, you almost never want the newline
        character. If you do want the newlines, access sys.stdin directly.
        
        stdin inherits the rest of its methods from sys.stdin, so you can use
        stdin.read() to get a string of all lines, if that's what you need.
        
        suppressing output and using statements
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        by default, pyfil prints the return value of expressions. Because this
        uses eval() internally to get value, statements may not be used. exec()
        supports statements, but it does not return the value of expressions
        when they are evaluated. When the -q/--quiet flag is used, automatic
        printing is suppressed, and expressions are evaluated with exec, so
        statements, such as assignments, may be used. Values may still be
        printed explicitly.
        
        looping over stdin
        ~~~~~~~~~~~~~~~~~~
        one can do simple loops with a generator expression. (note that any
        expression that evaluates to an iterator will print each item on a new
        line unless the ``--join`` option is specified.)
        
        .. code:: bash
        
            $ ls / | rep '(i.upper() for i in stdin)'
            BIN@
            BOOT/
            DEV/
            ETC/
            HOME/
            ...
        
        However, the ``-l``/``--loop`` flag rep loops over stdin in a context
        like this:
        
        .. code:: python
        
            for i in map(str.rstrip, sys.stdin):
                expressions
        
        Therefore, the above loop can also be written thusly:
        
        .. code:: bash
        
            $ ls / | rep -l 'i.upper()'
        
        ``--pre`` and ``--post`` (-b and -e) options can be used to specify
        actions to run before or after the loop. Note that the --pre option is
        run with exec instead of eval, and therefore output is never printed,
        and statements may be used. This is for things like initializing
        container types or importing additional libraries. --post is
        automatically printed and statements are not allowed (unless --quiet is
        used). --loop is implied if either of these options are used.
        
        Using ``-s``/``--split`` or ``-F``/``--field-sep`` for doing awk things
        also implies --loop. The resulting list is named ``f`` in the execution
        environment, in quazi-Perl fashion. (oh, and that list is actually a
        subclass of collections.UserList that returns an empty string if the
        index doesn't exist, so it acts more like awk with empty fields, rather
        than throwing and error and interrupting iteration).
        
        json
        ~~~~
        by popular demand, pyfil can parse json objects from stdin with the
        ``-j``/``--json`` flag. They are passed into the environment as the
        ``j`` object.  combining with the --loop flag will treat stdin as one json
        object per line.
        
        formatting output (and 'awk stuff')
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        It's probably obvious that the most powerful way to format strings is
        with Python's str.format method and the ``-F`` or ``-s`` options.
        
        .. code:: bash
        
          $ ls -l /|rep -s '"{0}\t{2}\t{8}".format(*f)'
          Error: tuple index out of range
          lrwxrwxrwx	root	bin
          drwxr-xr-x	root	boot/
          drwxr-xr-x	root	dev/
          drwxr-xr-x	root	etc/
          drwxr-xr-x	root	home/
          lrwxrwxrwx	root	lib
          ...
        
        However, you will note that using ``string.format(*f)`` produces an
        error and does not print anything to stdout (error message is sent to
        stderr; see error handling for more options) for lines without enough
        fields, which may not be the desired behavior when dealing with lines
        containing arbitrary numbers of fields.
        
        For simpler cases, you may wish to use the ``-n``/``--join`` option,
        which will join any iterables with the specified string before printing,
        and, in the case of the ``f`` list, will replace any none-existent
        fields with an empty string.
        
        .. code:: bash
        
          $ ls -l /|rep -sn '\t' 'f[0], f[2], f[8]'
          total		
          lrwxrwxrwx	root	bin
          drwxr-xr-x	root	boot/
          drwxr-xr-x	root	dev/
          drwxr-xr-x	root	etc/
          drwxr-xr-x	root	home/
          lrwxrwxrwx	root	lib
        
        In this case, the first line of ``ls -l /`` provides values for all
        available fields.
        
        Technical note:
            The separator specified with the ``--join`` option is implemented
            internally as ``ast.literal_eval("'''"+STRING.replace("'",
            r"\'")+"'''")``. If one works hard at it, it is possible to pass
            values which will cause pyfil to crash; i.e. patterns ending with a
            backslash. Keep in mind rules about escape sequences in the shell and
            in python if you absolutely must have a pattern that terminates with
            a backslash. (The reason it is implemented this way is to allow the
            use of escape sequences that are meaningful to the python, but not
            the shell, such as \\n, \\t, \\x, \\u, etc.)
        
        examples
        ~~~~~~~~
        
        *I realize that it's much better to do most of these things with the
        original utility. This is just to give some ideas of how to use `rep`*
        
        replace ``wc -l``:
        
        .. code:: bash
        
          $ ls / | rep 'len(stdin.l)'
          20
        
        replace ``fgrep``:
        
        .. code:: bash
        
          $ ls / | rep '(i for i in stdin if "v" in i)'
          $ ls / | rep -l 'i if "v" in i else None'
        
        
        replace ``grep``:
        
        .. code:: bash
        
          $ ls / | rep '(i for i in stdin if re.search("^m", i))'
          $ ls / | rep 'filter(lambda x: re.search("^m", x), stdin)'
        
        replace ``sed 's/...``:
        
        .. code:: bash
        
          $ ls / | rep -l 're.sub("^([^aeiou][aeiou][^aeiou]\W)", lambda m: m.group(0).upper(), i)'
          BIN@
          boot/
          data/
          DEV/
          etc/
          ...
        
        This example illustrates that, while you might normally prefer ``sed``
        for replacement tasks, the ability to define a replacement function with
        ``re.sub`` does offer some interesting possibilities. Indeed, someone
        familiar with coreutils should never prefer to do something they already
        comfortable doing the traditional way with ``rep`` (coreutils are
        heavily optimized). Python is interesting for this use-case because it
        offers great logic, anonymous functions and all kinds of other goodies
        that only full-fledged, modern programming language can offer. Use
        coreutiles for the jobs they were designed to excel in. Use ``rep`` to
        do whatever they can't... and seriously, how will coreutils do this?:
        
        .. code:: bash
        
          $ wget -qO- http://pypi.python.org/pypi/pyfil/json/ | rep -j 'j["urls"][0]["filename"]'
          pyfil-0.5-py3-none-any.whl
        
        
        Other things which might be difficult with coreutils:
        
        .. code:: bash
        
          $ ls / | rep -n '  ' 'reversed(stdin.l)'
          var/  usr/  tmp/  sys/  srv/  sbin@  run/  root/  proc/  opt/  ...
          $ # ^^ also, `ls /|rep -n '  ' 'stdin.l[::-1]'
          $
          $ 
        
        error handling
        ~~~~~~~~~~~~~~
        If pyfil encounters an exception while evaluating user input the default
        is to print the error message to stderr and continue (if looping over
        stdin), as we saw in the section on formatting output. However, errors
        can also be silenced entirely with the ``-S``/``--silence-errors``
        option. In the below example, the first line produces an error, but we
        don't hear about it.
        
        .. code:: bash
        
          $ ls -l /|rep -sS '"{0}\t{2}\t{8}".format(*f)' 
          lrwxrwxrwx	root	bin
          drwxr-xr-x	root	boot/
          drwxr-xr-x	root	dev/
          drwxr-xr-x	root	etc/
          drwxr-xr-x	root	home/
          lrwxrwxrwx	root	lib
          ...
        
        Alternatively, errors may be raised when encountered, which will stop
        execution and give a (fairly useless, in this case) traceback. This is
        done with the ``-R``/``--raise-errors`` flag.
        
        .. code:: bash
        
          $ ls -l /|rep -sR '"{0}\t{2}\t{8}".format(*f)'
          Traceback (most recent call last):
            File "/home/ninjaaron/src/py/pyfil/venv/bin/rep", line 9, in <module>
              load_entry_point('pyfil', 'console_scripts', 'rep')()
            File "/home/ninjaaron/src/py/pyfil/pyfil/pyfil.py", line 242, in main
              run(expressions, a, namespace)
            File "/home/ninjaaron/src/py/pyfil/pyfil/pyfil.py", line 164, in run
              handle_errors(e, args)
            File "/home/ninjaaron/src/py/pyfil/pyfil/pyfil.py", line 134, in handle_errors
              raise exception
            File "/home/ninjaaron/src/py/pyfil/pyfil/pyfil.py", line 162, in run
              value = func(expr, namespace)
            File "<string>", line 1, in <module>
          IndexError: tuple index out of range
        
        In addition to these two handlers, it is possible to specify a
        rudimentary custom handler with the ``-H``/``--exception-handler``
        flags. The syntax is ``-H 'Exception: expression'``, where ``Exception``
        can be any builtin exception class (including Exception, to catch all
        errors), and ``expression`` is the alternative expression to evaluate
        (and print, if not --quiet).
        
        .. code:: bash
        
          $ ls -l /|rep -sH 'IndexError: i' '"{0}\t{2}\t{8}".format(*f)'
          total 32
          lrwxrwxrwx	root	bin
          drwxr-xr-x	root	boot/
          drwxr-xr-x	root	dev/
          drwxr-xr-x	root	etc/
          drwxr-xr-x	root	home/
          lrwxrwxrwx	root	lib
          ...
        
        In this case, we've chosen to print line without any additional
        formatting. If other errors are encountered, it will fall back to other
        handlers (``-S``, ``-R``, or the default). For more sophisticated error
        handling... Write a real Python script, where you can handle to your
        heart's content.
        
        Also note that this case is possible to handle with a test instead of an
        exception handler because ``f`` is a special list that will return an
        empty string instead of throw an index error if the index is out of
        range:
        
        ``ls -l / | rep -s '"{0}\t{2}\t{8}".format(*f) if f[2] else i'``
        
        Easy-peasy.
        
Keywords: evaluate
Platform: UNKNOWN
