Metadata-Version: 1.1
Name: pyfil
Version: 1.9
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`` stands for PYthon FILter. One of the tenants of the `Unix
        design`_ is that every program is a filter. It's especially obvious of
        programs, like ``grep``, ``sed``, ``sort``, ``tr``, etc.
        
        One notable example is ``awk`` -- a Turing-complete, interpreted
        language for parsing text. While AWK scripts are still in use it's a
        fine language, it has been superseded for parsing script by more
        general languages like Perl and later Python and Ruby. However, AWK was
        designed to be especially useful in the shell as a filter, and it is
        still in very commonly used for that today (in part because it is on
        every \*nix system, but also because it's great at what it does). AWK is
        able to be any arbitrary text filter that doesn't come as a coreutil.
        ``perl -e`` is also quite good as a filter, and Ruby has made a valiant
        attempt to do so as well.
        
        While python does have a few good one-line uses (``python -m
        http.server``), some elements of its design make it less suited than the
        afore-mentioned languages. ``pyfil`` is one of several attempts to
        address this issue. In particular, it takes a lot of queues in the
        design of its CLI from AWK and Perl, and aims fundamentally to be a
        capable text filter, though it will evaluate any arbitrary Python
        expression and print its value (with modules being imported implicitly
        as required).
        
        As a more modern touch, it also has a special emphasis on
        interoperability with JSON. If the return value of the evaluated
        expression is a container type, python will attempt to serialize it as
        JSON before printing, so you can pipe output into other tools that deal
        with JSON, store it to a file for later use, or send it over http. This,
        combined with the ability to read JSON from stdin (with --json) make
        ``pyfil`` a good translator between the web, which tends to speak JSON
        these days, and the POSIX environment, which tends to think about data
        in terms of lines in a file (frequently with multiple fields per line).
        
        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
        
        .. _unix design: https://en.wikipedia.org/wiki/Unix_philosophy
        
        .. contents::
        
        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_
        - pyeval_
        - quickpy_
        
        Don't worry. I've stolen some of their best ideas already, and I will go
        on stealing as long as it takes!
        
        .. _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
        .. _pyeval: https://bitbucket.org/nejucomo/pyeval/wiki/Home
        .. _quickpy: https://github.com/slezica/quick-py
        
        usage
        -----
        
        .. code::
        
         pyfil [-h] [-l] [-x] [-q] [-j] [-o] [-b PRE] [-e POST] [-s] [-F PATTERN]
               [-n STRING] [-R] [-S] [-H EXCEPTION_HANDLER]
               expression [expression ...]
        
        positional arguments:
          expression            expression(s) to be executed. If multiple expression
                                arguments are given, and --exec is not used, the value
                                of the previous expression is available as 'x' in the
                                following expression. if --exec is used, all
                                assignment must be explicit.
        
        optional arguments:
          -h, --help            show this help message and exit
          -l, --loop            for n, i in enumerate(stdin): expressions
          -x, --exec            use exec instead of eval. statements are allowed, but
                                automatic printing is lost. doesn't affect --post
          -q, --quiet           suppress automatic printing. doesn't affect --post
          -j, --json            load stdin as json into object 'j'; If used with
                                --loop, treat each line of stdin as a new object
          -J, --real-dict-json  like -j, but creates real dictionaries instead of the
                                wrapper that allows dot syntax.
          -o, --force-oneline-json
                                outside of loops and iterators, objects serialzed to
                                json print with two-space indent. this forces this
                                forces all json objects to print on a single line.
          -b PRE, --pre PRE     statement to evaluate before expression args. multiple
                                statements may be combined with ';'. no automatic
                                printing
          -e POST, --post POST  expression to evaluate after the loop. always handeled
                                by eval, even if --exec, and always prints return
                                value, even if --quiet. implies --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 --loop
          -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
        ~~~~~~~~~~~~~~~~~
        ``pyfil`` automatically imports any modules used in expressions.
        
        If you'd like to create any other objects to use in the execution
        environment ~/.config/pyfil-env.py and put things in it.
        
        default objects:
        
        - l = []
        - d = {}
        
        These are empty containers you might wish to add items to during
        iteration, for example.
        
        - x is the value of the previous expression unless --exec was used.
        
        The execution environment also has a special object for stdin,
        creatively named ``stdin``. This differs from sys.stdin in that it
        strips trailing newlines when you iterate over it, and it has
        a property, ``stdin.l``, which returns a list of the lines (without
        newlines). 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.
        
        Certain other flags may create additional objects in the evaluation
        context.
        
          --loop (or anything that implies --loop) create ``n`` and ``i``.
          --json creates ``j``.
          --split or --field_sep create ``f``
          
        Check the flag descriptions for further details.
        
        output
        ~~~~~~
        automatic printing
        ..................
        By default, pyfil prints the return value of expressions. Different
        types of objects use different printing conventions.
        
        - ``None`` does not print (as in the REPL)
        - strings are sent directly to to ``print()``
        - iterators (not other iterables) print each item on a new line.
        - other objects are serialized as json. If an object cannot be
          serialized as json, it is sent directly to print().
        - all of these are overridden by --join
        
        Iterators will also try to serialize each returned object as json if
        they are not strings. json objects will be indented if only one object
        is being printed. If --loop is set or several of objects are being
        serialzed from an iterator, it will be one object per-line.
        --force-oneline-json extends this policy to printing single json objects
        as well.
        
        examples:
        
        .. code:: bash
        
          $ # None gets skipped
          $ pyfil None
          $ # strings and numbers just print
          $ pyfil sys.platfrom
          linux
          $ pyfil math.pi
          3.141592653589793
          $ # objects try to print as json
          $ pyfil sys.path
          [
            "/home/ninjaaron/.local/bin",
            "/usr/lib/python35.zip",
            "/usr/lib/python3.5",
            "/usr/lib/python3.5/plat-linux",
            "/usr/lib/python3.5/lib-dynload",
            "/home/ninjaaron/.local/lib/python3.5/site-packages",
            "/usr/lib/python3.5/site-packages"
          ]
          $ pyfil '{i: n for n, i in enumerate(sys.path)}'
          {
            "/usr/lib/python3.5/plat-linux": 3,
            "/usr/lib/python35.zip": 1,
            "/usr/lib/python3.5": 2,
            "/usr/lib/python3.5/lib-dynload": 4,
            "/usr/lib/python3.5/site-packages": 6,
            "/home/ninjaaron/.local/lib/python3.5/site-packages": 5,
            "/home/ninjaaron/.local/bin": 0
          }
          $ # unless they can't
          $ pyfil '[list, print, re]'
          [<class 'list'>, <built-in function print>, <module 're' from '/usr/lib/python3.5/re.py'>]
          $ # iterators print each item on a new line, applying the same conventions
          $ pyfil 'iter(sys.path)'
          /home/ninjaaron/src/py/pyfil/venv/bin
          /home/ninjaaron/src/py/pyfil
          /usr/lib/python35.zip
          /usr/lib/python3.5
          /usr/lib/python3.5/plat-linux
          /usr/lib/python3.5/lib-dynload
          /home/ninjaaron/src/py/pyfil/venv/lib/python3.5/site-package
          $ pyfil '(i.split('/')[1:] for i in sys.path)'
          ["home", "ninjaaron", "src", "py", "pyfil", "venv", "bin"]
          ["home", "ninjaaron", "src", "py", "pyfil"]
          ["usr", "lib", "python35.zip"]
          ["usr", "lib", "python3.5"]
          ["usr", "lib", "python3.5", "plat-linux"]
          ["usr", "lib", "python3.5", "lib-dynload"]
          ["home", "ninjaaron", "src", "py", "pyfil", "venv", "lib", "python3.5", "site-packages"]
        
        Most JSON is also valid Python, but be aware that you may occasionally
        see ``null`` instead of ``None`` along with ``true`` and ``false``
        instead of ``True`` and ``False``, and your tuples will look like list.
        I guess that's a risk I'm willing to take. (The rational for this is
        that pyfil, despite what the name of the ``rep`` command may indicate,
        is more about composability in the shell than printing valid Python
        literals. JSON is the defacto standard for serialization, or should be,
        if only people would stop using XML for that...)
        
        suppressing output and using statements
        .......................................
        Because these defaults use eval() internally to get value of
        expressions, statements may not be used. exec() supports statements, but
        it does not return the value of expressions when they are evaluated.
        When the -x/--exec 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.
        
        --quite suppresses automatic printing, but eval is still used.
        
        The --post option is immune from --quiet and --exec. It will always be
        evaluated with ``eval()``, and it will always try to print. The only
        difference is that if --quiet or --exec was used, json will be printed
        with indentation unless --force-oneline-json is used.
        
        using files for input and output
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        ``pyfil`` doesn't have any parameters for input and output files. Instead,
        use redirection.
        
        .. code:: bash
        
          pyfil -s 'i.upper()' > output.txt < input.txt
        
        using multiple expression arguments
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        ``pyfil`` can take as many expressions as desired as arguments. When used
        with --exec, this works pretty much as expected, and assignment must be
        done manually.
        
        Without --exec, the return value of each expression is assigned to the
        variable ``x``, which can be used in the next expression. The final
        value of ``x`` is what is ultimately printed, not any intermediate
        values.
        
        .. code:: bash
        
          $ pyfil 'reversed("abcd")' 'i.upper() for i in x'
          D
          C
          B
          A
        
        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 / | pyfil 'i.upper() for i in stdin'
            BIN@
            BOOT/
            DEV/
            ETC/
            HOME/
            ...
        
        However, with the ``-l``/``--loop`` flag, pyfil loops over stdin in a
        context like this:
        
        .. code:: python
        
            for n, i in enumerate(stdin):
                expressions
        
        Therefore, the above loop can also be written thusly:
        
        .. code:: bash
        
            $ ls / | pyfil -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. --post is automatically printed and statements are not
        allowed (even if --exec is used). --loop is implied if ``--post`` is
        used. ``--pre`` can be used without a --loop to do assignments (or
        whatever else you may want to do with a statement).
        
        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).
        
        json input
        ~~~~~~~~~~
        ``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. json objects support dot syntax for attribute access, e.g.
        ``j.someattr.attr_of_someattr``
        
        There are occasionally functions that require "real" dictionaries and
        won't work with this special subclass that supports dot access. In
        such cases, use ``-J``/``--real-dict-json`` to get unadultered Python
        dictionaries.
        
        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 /|pyfil -s '"{0}\t{2}\t{8}".format(*f)'
          IndexError: 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 /|pyfil -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 `pyfil`*
        
        replace ``wc -l``:
        
        .. code:: bash
        
          $ ls / | pyfil 'len(stdin.l)'
          20
        
        replace ``fgrep``:
        
        .. code:: bash
        
          $ ls / | pyfil '(i for i in stdin if "v" in i)'
          $ ls / | pyfil -l 'i if "v" in i else None'
        
        
        replace ``grep``:
        
        .. code:: bash
        
          $ ls / | pyfil 'filter(lambda x: re.search("^m", x), stdin)'
          $ ls / | pyfil -lS 're.search("^m", i).string)'
          $ # using the -S option to suppress a ton of error messages
        
        replace ``sed 's/...``:
        
        .. code:: bash
        
          $ ls / | pyfil -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 ``pyfil`` (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 ``pyfil`` to
        do whatever they can't... and seriously, how will coreutils do this?:
        
        .. code:: bash
        
          $ wget -qO- http://pypi.python.org/pypi/pyfil/json/ | pyfil -j 'j.urls[0].filename'
          pyfil-0.5-py3-none-any.whl
          $ ls -l | pyfil -qSs \
          "d.update({f[8]: {'permissions': f[0], 'user': f[2], 'group': f[3],
                            'size': int(f[4]), 'timestamp': ' '.join(f[5:8])}})" \
          --post 'd'
        .. code:: json
        
          {
            "README.rst": {
              "group": "users",
              "user": "ninjaaron",
              "permissions": "-rw-r--r--",
              "timestamp": "Sep 6 20:55",
              "size": 18498
            },
            "pyfil/": {
              "group": "users",
              "user": "ninjaaron",
              "permissions": "drwxr-xr-x",
              "timestamp": "Sep 6 20:20",
              "size": 16
            },
            "setup.py": {
              "group": "users",
              "user": "ninjaaron",
              "permissions": "-rw-r--r--",
              "timestamp": "Sep 6 20:30",
              "size": 705
            },
            "LICENSE": {
              "group": "users",
              "user": "ninjaaron",
              "permissions": "-rw-r--r--",
              "timestamp": "Sep 3 13:32",
              "size": 1306
            }
          }
        
        Other things which might be difficult with coreutils:
        
        .. code:: bash
        
          $ ls / | pyfil -n '  ' 'reversed(stdin.l)'
          var/  usr/  tmp/  sys/  srv/  sbin@  run/  root/  proc/  opt/  ...
          $ # ^^ also, `ls /|pyfil -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 /|pyfil -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 /|pyfil -sR '"{0}\t{2}\t{8}".format(*f)'
          Traceback (most recent call last):
            File "/home/ninjaaron/src/py/pyfil/venv/bin/pyfil", line 9, in <module>
              load_entry_point('pyfil', 'console_scripts', 'pyfil')()
            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 /|pyfil -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 / | pyfil -s '"{0}\t{2}\t{8}".format(*f) if f[2] else i'``
        
        Easy-peasy.
        
Keywords: evaluate
Platform: UNKNOWN
Classifier: Programming Language :: Python :: 3
