C'è un modo pitonico di sapere quando viene attraversato il primo e l'ultimo ciclo in un per essere passato?
-
28-10-2019 - |
Domanda
Ho un modello in cui ho messo, diciamo 5 moduli, ma tutti disabiliti per essere pubblicati tranne il primo. Il modulo successivo può essere compilato solo se faccio clic su un pulsante che lo consente prima.
Sto cercando un modo per implementare una variabile Templatetag Forloop.
Fondamentalmente quello che devo fare è qualcosa di simile:
for form_data in step.hashes:
# get and fill the current form with data in form_data
if not forloop.last:
# click the button that enables the next form
# submit all filled forms
Soluzione
Se capisco correttamente la tua domanda, vuoi un semplice test per se sei all'inizio o alla fine dell'elenco?
In tal caso, questo lo farebbe:
for item in list:
if item != list[-1]:
#Do stuff
Per il primo elemento nell'elenco, sostituiresti "-1" con 0.
Altri suggerimenti
Non so nulla di integrato, ma puoi facilmente scrivere un generatore per fornirti le informazioni richieste:
def firstlast(seq):
seq = iter(seq)
el = prev = next(seq)
is_first = True
for el in seq:
yield prev, is_first, False
is_first = False
prev = el
yield el, is_first, True
>>> list(firstlast(range(4)))
[(0, True, False), (1, False, False), (2, False, False), (3, False, True)]
>>> list(firstlast(range(0)))
[]
>>> list(firstlast(range(1)))
[(0, True, True)]
>>> list(firstlast(range(2)))
[(0, True, False), (1, False, True)]
>>> for count, is_first, is_last in firstlast(range(3)):
print(count, "first!" if is_first else "", "last!" if is_last else "")
0 first!
1
2 last!
Potresti usare enumerate
e confronta il contatore con la lunghezza dell'elenco:
for i, form_data in enumerate(step.hashes):
if i < len(step.hashes):
whatever()
for form_data in step.hashes[:-1]:
# get and fill the current form with data in form_data
for form_data in step.hashes[-1:]:
# get and fill the current form with data in form_data
# click the button that enables the next form
# submit all filled forms
Non mi piace la ripetizione di get and fill the current form with data in form_data
? Definire una funzione.
Generatore con buffer.
def first_last( iterable ):
i= iter(iterable)
f= next(i)
yield f, "first"
n= next(i)
for another in i:
yield n, None
n= another
yield n, "last"
for item, state in first_list( iterable ):
# state is "first", None or "last".
Zippando due sequenze
flags = ["first"] + (len(iterable)-2)*[None] + ["last"]
for item, state in zip( iterable, flags ):
# state is "first", None or "last".
Penso che voglia avere un wrapper attorno all'iteratore che fornisce prime / ultime query, anche il parametro potrebbe essere un iteratore, quindi ogni tipo di len () sarebbe fallito
Qui è quello che sono venuto finora, il trucco è usare un doppio iteratore, che guarda avanti un passo del primo:
class FirstLastIter(object):
def __init__(self, seq):
self._seq_iter = iter(seq)
self._seq_iter_next = iter(seq)
self._idx = -1
self._last = None
self.next_next()
@property
def first(self):
return self._idx == 0
@property
def last(self):
return self._last == True
def __iter__(self):
return self
def next_next(self):
try:
self._seq_iter_next.next()
except StopIteration:
self._last = True
def next(self):
val = self._seq_iter.next()
self._idx += 1
self.next_next()
return val
for x in FirstLastIter([]):
print x
iterator = FirstLastIter([1])
for x in iterator:
print x,iterator.first,iterator.last
iterator = FirstLastIter([1,2,3])
for x in iterator:
print x,iterator.first,iterator.last
ritorna:
1 True True
1 True False
2 False False
3 False True
Prima che qualcuno vada a affilare le loro torce o accendendo le forze del tono, non sono un esperto in quello che è Divinatorio, questo affermato, mi sembra che se first
e/o last
è ricercato da un elenco, al di if first
o if last
All'interno di un ciclo, sembra previsto super
la classe e il componente aggiuntivo della funzionalità che si desidera ... forse, quindi ciò che segue è la versione totalmente pre-alfa E-1^11% di tipo che può causare il caos se esaminato il martedì nel modo giusto. .
import sys
## Prevent `.pyc` (Python byte code) files from being generated
sys.dont_write_bytecode = True
from collections import OrderedDict
class MetaList(list):
"""
Generates list of metadata dictionaries for list types
## Useful resources
- [C Source for list](https://github.com/python/cpython/blob/master/Objects/listobject.c)
- [Supering `list` and `collections.MutableSequence`](https://stackoverflow.com/a/38446773/2632107)
"""
# List supering methods; maybe buggy but seem to work so far...
def __init__(self, iterable = [], **kwargs):
"""
> Could not find what built in `list()` calls the initialized lists during init... might just be `self`...
> If feeling cleverer check the C source. For now this class will keep a copy
## License [GNU_GPL-2](https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html)
Generates list of metadata dictionaries for lists types
Copyright (C) 2019 S0AndS0
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; version 2
of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
"""
self.metadata = []
for index, value in enumerate(iterable):
if isinstance(value, list):
sub_kwargs = {}
sub_kwargs.update(kwargs)
sub_kwargs['address'] = kwargs.get('address', [index])
sub_list = MetaList(iterable = value, **sub_kwargs)
self.append(sub_list, **kwargs)
else:
self.append(value, **kwargs)
# Note; supering order matters when using built in methods during init
super(MetaList, self).__init__(iterable)
def __add__(self, other):
"""
Called when adding one list to another, eg `MetaList([1,2,3]) + [9,8,7]`
- Returns copy of list plus `other`, sorta like `self.extend` but without mutation
## Example input
test_list = MetaList([1 ,2, 3])
longer_list = test_list + [4, 5, 6]
## Example output
print("#\ttest_list -> {0}".format(test_list))
# test_list -> [1, 2, 3]
print("#\tlonger_list -> {0}".format(longer_list))
# longer_list -> [1, 2, 3, 4, 5, 6]
"""
super(MetaList, self).__add__(other)
output = MetaList(self)
output.extend(other)
return output
def __setitem__(self, index, item, **kwargs):
"""
Called when setting values by index, eg `listing[0] = 'value'`, this updates `self` and `self.metadata`
"""
super(MetaList, self).__setitem__(index, item)
address = kwargs.get('address', []) + [index]
value = item
dictionary = self.__return_dictionary(
address = address,
index = index,
value = value)
self.metadata[index] = dictionary
self.__refresh_first()
self.__refresh_last()
self.__refresh_indexes(start = index)
def append(self, item, **kwargs):
"""
Appends to `self.metadata` an `OrderedDict` with the following keys
- `address`: `[0]` or `[0, 1, 5]` list of indexes mapping to `value`
- `index`: `0` or `42` integer of index within current listing
- `value`: `string`, `['list']`, `{'dict': 'val'}`, etc; not enabled by default
- `first`: `True`/`False` boolean; item is first in current listing
- `last`: `True`/`False` boolean; item is last in current listing
"""
super(MetaList, self).append(item)
# Update last status of previously last item within `self.metadata`
if self.metadata:
self.metadata[-1]['last'] = False
index = len(self.metadata)
address = kwargs.get('address', []) + [index]
value = item
dictionary = self.__return_dictionary(
address = address,
index = index,
value = value)
dictionary['first'] = False
dictionary['last'] = True
if len(self.metadata) == 0:
dictionary['first'] = True
self.metadata += [dictionary]
def extend(self, listing, **kwargs):
"""
Extends `self.metadata` with data built from passed `listing`
- Returns: `None`
> `kwargs` is passed to `MetaList` when transmuting list types
"""
super(MetaList, self).extend(listing)
for index, value in enumerate(listing):
if isinstance(value, list):
last_address = []
if self.metadata:
# Grab `address` list minus last item
last_address = self.metadata[-1]['address'][0:-1]
# Add this `index` to `address` list for recursing
sub_list = MetaList(value, address = last_address + [index], **kwargs)
self.append(sub_list, **kwargs)
else:
self.append(value, **kwargs)
def insert(self, index, item, **kwargs):
"""
Inserts `item` at `index` for `self` and dictionary into `self.metadata`
- Returns: `None`
Note: `self.metadata[index + 1]` have the following data mutated
- `data['index']`
- `data['address']`
Additionally: `self.metadata[0]` and `self.metadata[-1]` data mutations will occur
- `data['first']`
- `data['last']`
"""
super(MetaList, self).insert(index, item)
address = kwargs.get('address', []) + [index]
dictionary = self.__return_dictionary(
address = address,
index = index,
value = item,
**kwargs)
self.metadata.insert(index, dictionary)
self.__refresh_first()
self.__refresh_last()
self.__refresh_indexes(start = index)
# Off-set to avoid n +- 1 errors ;-)
self.__refresh_addresses(
start = index + 1,
index = len(address) - 1,
modifier = 1)
def pop(self, index = -1, target = None):
"""
Pop value from `self` and `self.metadata`, at `index`
- Returns: `self.pop(i)` or `self.metadata.pop(i)` depending on `target`
"""
popped_self = super(MetaList, self).pop(index)
popped_meta = self.__pop_metadata(index)
if 'metadata' in target.lower():
return popped_meta
return popped_self
def remove(self, value):
"""
Removes `value` from `self` and `self.metadata` lists
- Returns: `None`
- Raises: `ValueError` if value does not exsist within `self` or `self.metadata` lists
"""
super(MetaList, self).remove(value)
productive = False
for data in self.metadata:
if data['value'] == value:
productive = True
self.__pop_metadata(data['index'])
break
if not productive:
raise ValueError("value not found in MetaList.metadata values")
# Special herbs and spices for keeping the metadata fresh
def __pop_metadata(self, index = -1):
"""
Pops `index` from `self.metadata` listing, last item if no `index` was passed
- Returns: `<dictionary>`
- Raises: `IndexError` if `index` is outside of listed range
"""
popped_metadata = self.metadata.pop(index)
addr_index = len(popped_metadata['address']) - 1
## Update values within `self.metadata` dictionaries
self.__refresh_first()
self.__refresh_last()
self.__refresh_indexes(start = index)
self.__refresh_addresses(start = index, index = addr_index, modifier = -1)
return popped_metadata
def __return_dictionary(self, address, index, value, **kwargs):
"""
Returns dictionaries for use in `self.metadata` that contains;
- `address`: list of indexes leading to nested value, eg `[0, 4, 2]`
- `index`: integer of where value is stored in current listing
- `value`: Duck!... Note list types will be converted to `MetaList`
- `first`: boolean `False` by default
- `last`: boolean `False` by default
> `kwargs`: passes through to `MetaList` if transmuting a list `value`
"""
if isinstance(value, list):
kwargs['address'] = address
value = MetaList(value, **kwargs)
dictionary = OrderedDict()
dictionary['address'] = address
dictionary['index'] = index
dictionary['value'] = value
dictionary['first'] = False
dictionary['last'] = False
return dictionary
def __refresh_indexes(self, start = 0):
"""
Update indexes from `start` till the last
- Returns: `None`
"""
for i in range(start, len(self.metadata)):
self.metadata[i]['index'] = i
def __refresh_addresses(self, start = 0, end = None, index = 0, modifier = -1):
"""
Updates `address`es within `self.metadata` recursively
- Returns: `None`
- Raises: `TODO`
> `index` is the *depth* within `address` that `modifier` will be applied to
"""
if not start or start < 0:
start = 0
if not end or end > len(self.metadata):
end = len(self.metadata)
for i in range(start, end):
metadata = self.metadata[i]
if isinstance(metadata['value'], list):
metadata['value'].__refresh_addresses(index = index, modifier = modifier)
else:
if len(metadata['address']) - 1 >= index:
metadata['address'][index] += modifier
else:
raise Exception("# TODO: __refresh_addresses append or extend address list")
def __refresh_last(self, quick = True):
"""
Sets/re-sets `self.metadata` `last` value
- Returns `True`/`False` based on if `self.metadata` was touched
If `quick` is `False` all items in current listing will be touched
If `quick` is `True` only the last item and second to last items are touched
"""
if not self.metadata:
return False
if len(self.metadata) > 1:
self.metadata[-2]['last'] = False
if not quick and len(self.metadata) > 1:
for i in range(0, len(self.metadata) - 1):
self.metadata[i]['last'] = False
self.metadata[-1]['last'] = True
return True
def __refresh_first(self, quick = True):
"""
Sets first dictionary within `self.metadata` `first` key to `True`
- Returns `True`/`False` based on if `self.metadata` was touched
If `quick` is `False` all items will be touched in current listing
If `quick` is `True` the first and second items are updated
"""
if not self.metadata:
return False
if len(self.metadata) > 1:
self.metadata[1]['first'] = False
if not quick and len(self.metadata) > 1:
for i in range(1, len(self.metadata)):
self.metadata[i]['first'] = False
self.metadata[0]['first'] = True
return True
# Stuff to play with
def deep_get(self, indexes, iterable = None):
"""
Loops over `indexes` returning inner list or value from `self.metadata`
- `indexes` list of indexes, eg `[1, 3, 2]`
- `iterable` maybe list, if not provided `self.metadata` is searched
"""
referance = self.metadata
if iterable:
reference = iterable
for index in indexes:
reference = reference[index]
return reference
def copy_metadata(self):
"""
Returns copy of `self.metadata`
"""
return list(self.metadata)
def yield_metadata(self, iterable = None, skip = {'first': False, 'last': False, 'between': False}, **kwargs):
"""
Yields a *flat* representation of `self.metadata`,
Prefilter via `skip = {}` dictionary with the following data
- `first`: boolean, if `True` skips items that are first
- `last`: boolean, if `True` skips items that are last
- `between`: boolean, if `True` skips items that are not last or first
"""
metadata = self.metadata
if iterable:
metadata = MetaList(iterable).metadata
for item in metadata:
if isinstance(item.get('value'), list):
# Recurse thy self
for data in item['value'].yield_metadata(skip = skip, **kwargs):
yield data
else:
if skip:
if skip.get('first', False) and item['first']:
continue
if skip.get('last', False) and item['last']:
continue
if skip.get('between', False) and not item['first'] and not item['last']:
continue
# If not skipped get to yielding
yield item
... e forse è più folle delle lampade di quell'amico che ha parlato pubblicamente di incontri ravvicinati, sanno chi sono ... ma questo fa alcuni trucchi eleganti
Esempio Input One
meta_list = MetaList([1, 2, 3, 4, 5])
for data in meta_list.metadata:
if data['first']:
continue
if data['last']:
continue
print("self[{0}] -> {1}".format(data['index'], data['value']))
Esempio di output uno
self[1] -> 2
self[2] -> 3
self[3] -> 4
Esempio input due
meta_list = MetaList(['item one', ['sub item one', ('sub', 'tuple'), [1, 2, 3], {'key': 'val'}], 'item two'])
for data in meta_list.yield_metadata():
address = "".join(["[{0}]".format(x) for x in data.get('address')])
value = data.get('value')
print("meta_list{0} -> {1} <- first: {2} | last: {3}".format(address, value, data['first'], data['last']))
Esempio di output due
meta_list[0] -> item one <- first: True | last: False
meta_list[1][0] -> sub item one <- first: True | last: False
meta_list[1][1] -> ('sub', 'tuple') <- first: False | last: False
meta_list[1][2][0] -> 1 <- first: True | last: False
meta_list[1][2][1] -> 2 <- first: False | last: False
meta_list[1][2][2] -> 3 <- first: False | last: True
meta_list[1][3] -> {'key': 'val'} <- first: False | last: True
meta_list[2] -> item two <- first: False | last: True
Se senti che il tuo cervello vanno tutti i menta freschi, ma un po 'non va tutto bene e questo è a modo suo tanto meglio ... per me è il massimo Divinatorio
Divertiti, e forse se ci sarà interesse spingerò questo a Github per tutti da tirare e forchetta.
Nota a margine @fabriziom +1 per un uso superbo di
@property
Magie