Various python snippets

snippets.py

"""
The MIT License (MIT)

Copyright (c) 2016, Ruslan Zhenetl

Permission is hereby granted, free of charge, to any person obtaining a copy 
of this software and associated documentation files (the "Software"), to deal 
in the Software without restriction, including without limitation the rights 
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
copies of the Software, and to permit persons to whom the Software is 
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all 
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.
"""
import re
import shelve
from collections import namedtuple, defaultdict
from datetime import datetime
from itertools import groupby
from operator import itemgetter

import click
import paramiko
from six.moves.urllib.parse import urlparse


class ObjectFab(object):
    """
    Simple and dirty memoized class constructor for ipython notebook or 
    fast hacking.
    >>> ObjectFab(x=1, y=2)
    YXNamedTuple(y=2, x=1)
    >>> ObjectFab('Point', x=1, y=2)
    Point(y=2, x=1)
    """
    instances = {}

    def __new__(cls, _class_name=None, **kwargs):
        name = (
            _class_name or
            ''.join(k.capitalize() for k in kwargs.keys()) + 'NamedTuple'
        )
        return cls.instances.setdefault(
            name, namedtuple(name, kwargs.keys())
        )(**kwargs)


def parse_indented(text):
    """
    >>> parse_indented('''
    ... a
    ...    b
    ... ''')
    [{'name': 'a', 'children': [{'name': 'b', 'children': []}]}]
    """
    prepared_lines = (l.expandtabs() for l in text.splitlines() if l.strip())
    grouped = groupby(prepared_lines, lambda s: len(s) - len(s.lstrip(' ')))

    stack = [[]]
    indents = [-1]

    for indent, names in grouped:
        while indent <= indents[-1]:
            stack = stack[:-1]
            indents.pop()
        indents.append(indent)

        stack[-1].extend({
            'name': name.strip(),
            'children': [],
        } for name in names)
        stack.append(stack[-1][-1]['children'])
        
    return stack[0]


class shelve_cache(object):
    """
    @shelve_cache
    def my_heavy_function():
    ...
    @shelve_cache('cache_file_name.shelve')
    def my_heavy_function():
    ...
    """
    def _set_func(self, func):
        self.func = func
        return self
    
    def __new__(cls, arg):
        instance = super(shelve_cache, cls).__new__(cls)
        if callable(arg):
            instance._set_func(arg)
            name = 'cache_{}.shelve'.format(arg.__name__)
            instance.cache = shelve.open(name)
            return instance
        else:
            instance.cache = shelve.open(arg)
            return instance._set_func
        
    def __call__(self, *args, **kwargs):
        key = self.make_key(*args, **kwargs)
        if key in self.cache:
            return self.cache[key][0]

        result = self.func(*args, **kwargs)
        self.cache[key] = result, datetime.now()
        self.cache.sync()
        return result

    @staticmethod
    def make_key(*args, **kwargs):
        return str((args, kwargs))

    
def get_nested(dict_, path):
    """
    >>> get_nested({'a': {'b': 1}}, ['a', 'b'])
    1
    """
    return reduce(lambda d, key: d[key], path, dict_)


def squash_dicts(dicts, **operations):
    """
    >>> squash_dicts([{'a': {'c': 1}}, {'a': {'c': 2}, 'b': 3}], a__c=sum)
    {'a': {'c': 3}, 'b': 3}
    """
    result = dicts[0].copy()
    for dict_ in dicts[1:]:
        result.update(dict_)

    for path_string, operation in operations.items():
        path = path_string.split('__')
        aggregated = operation(get_nested(d, path) for d in dicts)
        get_nested(result, path[:-1])[path[-1]] = aggregated

    return result


def group_by(iterable, key):
    groups = {}
    for item in iterable:
        groups.setdefault(key(item), []).append(item)
    return groups


def join(left, right, **conditions):
    l_index = itemgetter(*conditions.keys())
    r_index = itemgetter(*conditions.values())

    right_indexed = {r_index(r): r for r in right}

    return [dict(l, **right_indexed[l_index(l)]) for l in left]


@contextmanager
def sftp_open(url_string, mode='r', key_filename=None, timeout=None):
    """Implements interface similar to __builtin__.open

    :param str path: 'ssh://{user}:{password}@{host}/{path}'
    :raises IOError

    >>> with sftp_open('ssh://user:password@host/path/filename.ext') as f:
    >>>    content = f.read()
    ...
    >>> with sftp_open('ssh://user:password@host/path/filename.ext', 'w') as f:
    >>>    f.write('content')
    ...
    """
    url = urlparse(url_string if '//' in url_string else '//' + url_string)

    with paramiko.SSHClient() as ssh:
        ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        ssh.connect(
            hostname=url.hostname, port=url.port, username=url.username,
            password=url.password, key_filename=key_filename, timeout=timeout,
        )
        with ssh.open_sftp() as sftp:
            with sftp.file(url.path, mode) as f:
                yield f


def ascii_table(model_list):
    table = [model_list[0].keys()] + [m.values() for m in model_list]
    lengths = map(lambda col: max(len(str(cell)) for cell in col), zip(*table))
    template = ' | '.join('{{:<{}}}'.format(l) for l in lengths)
    return '\n'.join(template.format(*r) for r in table)


class InspectedFunc(object):
    re_params = re.compile('[ ]*:param (\w+): (.+)')

    def __init__(self, func):
        self.varnames = func.__code__.co_varnames[:func.__code__.co_argcount]
        self.descriptions = dict(self.re_params.findall(func.__doc__ or ''))
        self.defaults = dict(zip(
            reversed(self.varnames), reversed(func.__defaults__ or [])
        ))


class Autocommand(object):
    def __init__(self, group, config={}):
        """
        @click.group()
        def cli(): pass

        autocommand = Autocommand(cli)

        @autocommand
        def(param_name: type):
            '''command help

            :param param_name: help text
            '''
        """
        self.group = group
        self.config = defaultdict(dict)
        self.config.update(config)

    def __call__(self, command_name=None):
        def register(func):
            inspected = InspectedFunc(func)
            defaults = inspected.defaults.copy()
            defaults.update(self.config['defaults'].get(func.__name__, {}))

            used = set()
            for name in inspected.varnames:
                chars = name[0] + name.capitalize()
                char = next((c for c in chars if c not in used), None)
                used.add(char)

                click.option(
                    '-' + char,
                    '--' + name,
                    default=defaults.get(name),
                    type=func.__annotations__.get(name),
                    help=inspected.descriptions.get(name, ''),
                    prompt=name not in defaults,
                )(func)

            self.group.command(
                self.config['command_names'].get(func.__name__) or command_name
            )(func)
            return func
        return register


if __name__ == '__main__':
    import doctest
    doctest.testmod()