Python Utils

utils.py

#########################################################
# Generic methods independent of any App logic here.
# This module is meant to be a Python tool set.
#########################################################

from itertools import chain, groupby
from operator import attrgetter
from contextlib import contextmanager
from inspect import ismethod
import re
from datetime import datetime, timedelta
from decimal import Decimal
import uuid
import os
from werkzeug.utils import secure_filename
import math
from flask import current_app


EMAIL_REGEX = re.compile(r"[^@]+@[^@]+\.[^@]+")


def union(list_of_lists):
    return list(set.union(*[set(l) for l in list_of_lists]))


def intersection(list_of_lists):
    return list(set.intersection(*[set(l) for l in list_of_lists]))


def difference(list1, list2):
    return list(set(list1).difference(set(list2)))


def random_string(length=None):
    string = str(uuid.uuid4()).replace('-', '')
    if length:
        string = string[:length]
    return string


def npartition(string, n=1, delimiter=' '):
    """
    Similar to python's built in partition method. But will
    split at the nth occurence of delimiter
    """
    groups = string.split(delimiter)
    return (delimiter.join(groups[:n]), delimiter, delimiter.join(groups[n:]))


def percentage(numerator, denominator):
    value = float(numerator)*100/float(denominator)
    return math.ceil(value*100)/100


def generate_unique_file_name(seed_name):
    return "%s_%s_%s" % (ist_now().strftime("%Y%m%d_%H%M%S%f"),
                         uuid.uuid4().hex[0:6],
                         secure_filename(seed_name))


def save_with_unique_name(_file, location):
    filename = generate_unique_file_name(_file.filename)
    _file.save(os.path.join(location, filename))
    return (filename, _file)


def is_email(mailstr):
    """
    Checks if a string matches the Email regex
    """
    return ((isinstance(mailstr, str) or isinstance(mailstr, unicode))
            and bool(EMAIL_REGEX.match(mailstr)))


def place_nulls(key, input_keyvals, output_results):
    """
    Useful in a specific case when you want to verify that a mapped list
    object returns objects corresponding to input list.
    Hypothetical example:
    Customer.raw_get_all([1,2,3]) returns [C1, C3]
    There is no customer with id 2 in db. But this is bad for us becaause
    we will want to iterate like zip (input, output) if possible. So we
    need to place nulls wherever the list is missing an output value. This
    function will make the list as [C1, None, C3]
    """
    if len(input_keyvals) != len(output_results):
        for index, keyval in enumerate(input_keyvals):
            try:
                if getattr(output_results[index], key) != keyval:
                    output_results.insert(index, None)
            except IndexError:
                output_results.insert(index, None)
    return output_results


def subdict(dictionary, keys):
    """
    >>>a={1:3, 4:5, 6:7}
    >>>subdict(a, [4,6])
    {4: 5, 6: 7}
    """
    return (dict((k, dictionary[k]) for k in keys if k in dictionary)
            if len(keys) > 0 else dictionary)


def add_kv_to_dict(dictionary, key, value):
    """
    >>> a={1:3, 4:5, 6:7}
    >>> add_kv_to_dict(a, 6, 9)
    {1: 3, 4: 5, 6: 9}
    """
    return dict(chain(dictionary.items(), [(key, value)]))


def merge(dict1, dict2):
    """
    >>> a={1:2, 3:4}
    >>> b={5:6, 7:8}
    >>> merge(a,b)
    {1: 2, 3: 4, 5: 6, 7: 8}
    """
    return dict(chain(dict1.iteritems(), dict2.iteritems()))


def add_kv_if_absent(dictionary, key, value):
        if key not in dictionary:
            dictionary[key] = value
        return dictionary


def has_duplicates(l):
    return len(l) != len(set(l))


def monetize(number):
    """
    Function used for rounding off numbers to a fixed number of
    places.
    >>> monetize(3.4389)
    Decimal('3.44')
    >>> monetize(3.4334)
    Decimal('3.43')
    """
    return Decimal(number).quantize(Decimal('.01'))


def sanitize(source_dict, whitelist, additional_params={}, keys_to_modify={},
             value_filterer=lambda v: False):
    """
    >>> raw={'name': 'surya', 'email': '[email protected]', 'bad_param': '<SCRIPT></SCRIPT>'}
    >>> raw={'name': 'surya', 'email': '[email protected]', 'bad_param': '<SCRIPT></SCRIPT>', 'postalcode': '55544'}
    >>> sanitize(raw, whitelist=['name', 'email', 'postalcode'], additional_params={'state': 'Wyoming', 'country': 'US'}, keys_to_modify={'postalcode':'zipcode'})
    {'email': '[email protected]', 'state': 'Wyoming', 'country': 'US', 'zipcode': '55544', 'name': 'surya'}
    """
    items = source_dict.items()
    for k, v in items:
        if k not in whitelist or value_filterer(v):
            del source_dict[k]
        elif k in keys_to_modify:
            source_dict[keys_to_modify[k]] = v
            del source_dict[k]

    return merge(source_dict, additional_params)


def is_int(s):
    if isinstance(s, int):
        return True
    else:
        try:
            int(s)
            return True
        except:
            return False


def flatten(list_of_lists):
    """
    >>> flatten([[1,2], [3,4,5]])
    [1, 2, 3, 4, 5]
    """
    return [item for sublist in list_of_lists for item in sublist]


def filtered_list(olist, exclude_list):
    return filter(lambda i:  i not in exclude_list, olist)


def getattr_safe(obj, attr):
    attr = getattr(obj, attr)
    if ismethod(attr):
        return attr()
    return attr


def serialize_attrs(obj, *args):
    """
    >>> serialize_attrs(Customer.first(), 'id', 'email')
    {'id': 1L, 'email': u'[email protected]'}
    """
    return dict((arg, getattr_safe(obj, arg)) for arg in args)


def grouplist(olist, key):
    """
    >>> customers
    [[email protected], [email protected], [email protected], [email protected], [email protected]]
    >>> customers[0].city="Delhi"
    >>> customers[1].city="Delhi"
    >>> customers[2].city="Mumbai"
    >>> customers[3].city="Mumbai"
    >>> customers[4].city="Chennai"
    >>> grouplist(customers, 'city')
    {'Chennai': [[email protected]],
     'Delhi': [[email protected], [email protected]],
     'Mumbai': [[email protected], [email protected]]}
    """
    return dict(
        (k, list(items))
        for k, items in group(olist, key))


def group(olist, key):
    """
    Same functionality as grouplist. But returns iterator instead of list
    """
    return groupby(olist, key=attrgetter(key))


def deep_group(olist, keys, sort_attr=None, serializer=None,
               attr_to_show=None,
               serializer_args=[], serializer_kwargs={},
               strip_single_object_lists=False):
    """
    >>> customers[0].country="India"
    >>> customers[0].state="UP"
    >>> customers[0].city="Delhi"
    >>> customers[1].country="India"
    >>> customers[1].state="UP"
    >>> customers[1].city="Delhi"
    >>> customers[2].country="India"
    >>> customers[2].state="UP"
    >>> customers[2].city="Agra"
    >>> customers[3].country="India"
    >>> customers[3].state="TN"
    >>> customers[3].city="Chennai"
    >>> customers[4].country="China"
    >>> customers[4].state="Tibet"
    >>> customers[4].city="Lhasa"
    >>> deep_group(customers, keys=['country', 'state', 'city'])
    {'China': {'Tibet': {'Lhasa': [[email protected]]}},
     'India': {'TN': {'Chennai': [[email protected]]},
               'UP': {'Delhi': [[email protected], [email protected]],
               'Agra': [[email protected]]}}}
    """
    if len(keys) == 0:
        return olist
    if sort_attr:
        olist.sort(key=attrgetter(sort_attr))
    result = {}
    for k, items in group(olist, keys[0]):
        items = list(items)
        if len(keys) == 1:
            if strip_single_object_lists and len(items) == 1:
                if serializer:
                    result[k] = getattr(
                        items[0], serializer)(*serializer_args,
                                              **serializer_kwargs)
                elif attr_to_show:
                    result[k] = getattr(
                        items[0], attr_to_show)
                else:
                    result[k] = items[0]
            else:
                if serializer:
                    result[k] = [getattr(
                        item, serializer)(*serializer_args,
                                          **serializer_kwargs)
                        for item in items]
                elif attr_to_show:
                    result[k] = [getattr(
                        items, attr_to_show) for item in items]
                else:
                    result[k] = items
        else:
            result[k] = deep_group(
                items, keys[1:],
                serializer=serializer,
                serializer_args=serializer_args,
                serializer_kwargs=serializer_kwargs,
                strip_single_object_lists=strip_single_object_lists)
    return result


def strip_bad_chars(string, chars=[' ', '_', ';', ',', '"', "'"]):
    for char in chars:
        string = string.replace(char, '')
    return string


def append_if_absent(l, i):
    if i not in l:
        l.append(i)
    return l


def add_to_list_in_dict(item, list_name, dictionary):
    append_if_absent(set_if_absent_and_get(dictionary, list_name, []), item)


@contextmanager
def use_and_throw(d, k):
    if k in d:
        yield getattr(d, k)
        del d.k


def unix_time(dt):
    epoch = datetime.utcfromtimestamp(0)
    delta = dt - epoch
    return delta.total_seconds()


def unix_time_millis(dt):
    return int(unix_time(dt) * 1000)


def ist_now():
    return datetime.utcnow()+timedelta(minutes=330)


def local_time():
    return datetime.utcnow() + timedelta(minutes=current_app.config[
        'TIME_DELTA'])


def public_dict(obj):
    d = dict((k, v) for k, v in obj.__dict__.iteritems()
             if not k.startswith('_'))
    return d


def pop_items(l):
    while len(l) > 0:
        yield l.pop()


def putdict(d, k, dv):
    if k not in d:
        d[k] = dv
    return d[k]


def set_if_absent_and_get(d, k, dv):
    if k not in d:
        setattr(d, k, dv)
    return getattr(d, k)


def get_if(obj, attr):
    return getattr(obj, attr) if obj else None

def join(words, delimiter=","):
    return delimiter.join([str(w)for w in words if w is not None])


def abbreviated_name(name, append_digit=None):
    """
    Returns a readable abbreviated name by removing vowels from the middle of
    the string and keeping the first and last letters of words.
    The final result is trimmed to 6 characters
    >>>abbreviated_name("I convert caffeine to code")
    'ICNVRT'
    """
    vowels = ['A', 'E', 'I', 'O', 'U']

    def words_of(name):
        return name.split()

    def strip_vowels(word):
        if len(word) > 2:
            return word[0]+filter(lambda l:
                                  l not in vowels, word[1:-1]) + word[-1]
        else:
            return word

    concatenate = ''.join

    abbr = concatenate([strip_vowels(word) for word in words_of(
        name.upper())])[0:6]

    if append_digit:
        abbr = abbr+str(append_digit)

    return abbr