Autovivification means implicitly creating data structures accessed via name when explicitly creating their data, such as initializing a hash upon assigning the first key/value pair, or creating a folder upon saving a file in a new path.
Questions tagged [autovivification]
75 questions
2
votes
3 answers
How to nonvivificate in Perl
Let's say I have a Perl script that does:
my $hash = {};
$hash->{'a'} = {aa => 'b'};
$hash->{'b'} = undef;
for (qw(a b c)) {
if(defined $hash->{$_}->{aa})
{
say "defined $_";
}
else
{
say "undef $_";
…
Eric Fossum
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1
vote
0 answers
problem loading Autovivification file when moving from python 2.7 to 3.6, KeyError: 'DictType'
In python 2.7, I have a bunch of files stored as the following object:
class AutoVivification(dict):
"""Implementation of perl's autovivification feature."""
def __getitem__(self, item):
try:
return…
jason
- 3,811
- 18
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- 147
1
vote
1 answer
Why autovivification works at 'for'?
I have next code:
print for @{ $events->{ $name } };
When $events is empty hash I got $name key which value is empty array []
Why autovivification works despite on that I just access element and assign nothing to it?
Eugen Konkov
- 22,193
- 17
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- 158
1
vote
2 answers
Is there autovivification for Go?
Is there autovivification for Go?
As @JimB correctly noticed, my definition is not that strict. About my goal: In Python we have a very elegant "emulation" for an autovivification:
class Path(dict):
def __missing__(self, key):
value…
Michael Dorner
- 17,587
- 13
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- 117
1
vote
3 answers
Generic autovivify function for Maps
How can I create vivify a key with generics? This code does not even compile:
/* populate the map with a new value if the key is not in the map */
private boolean autoVivify(Map map, K key)
{
if (! map.containsKey(key))
{
…
perreal
- 94,503
- 21
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1
vote
3 answers
How to handle combination []+= for auto-vivifying hash in Ruby?
In order to implement auto-vivification of Ruby hash, one can employ the following class
class AutoHash < Hash
def initialize(*args)
super()
@update, @update_index = args[0][:update], args[0][:update_key] unless
args.empty?
end
def…
Andrei
- 10,918
- 12
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- 110
1
vote
1 answer
Multiple initialization of auto-vivifying hashes using a new operator in Ruby
I would like to initialize several auto-vivifying hashes by one-line expression. So far I came to an extra method for the AutoHash object:
class AutoHash < Hash
...
def few(n=0)
Array.new(n) { AutoHash.new }
end
which allows me to do the…
Andrei
- 10,918
- 12
- 76
- 110
1
vote
1 answer
Python One-Line Tree using defaultdict. How to reduce the number of arguments required?
I'm using this gist's defaultdict one-line tree.
def tree(): return defaultdict(tree)
Currently, you must provide a separate [] for every node you want to add.
ie:
users =…
JmsBtlr111
- 31
- 1
- 5
1
vote
1 answer
Can't locate autovivification.pm in @INC
I get the following error when I run my Perl script:
"Can't locate autovivification.pm in @INC"
How can I install this module on my system?
Poisson
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1
vote
2 answers
Perl defining undefined keys
The following code prints Key defined 3.
Why is Perl defining the key ABC ? I was expecting all the three checks to be false.What am I doing incorrectly ?
#!/usr/bin/perl
use warnings;
use strict;
my %Hash;
if(defined $Hash{'ABC'})
{
…
Jean
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1
vote
3 answers
Perl Hashref initialize and assign at once
Actually I found a weird behavior when i try to initialize a Perl Hash(ref) and try to assign it via autovivication at once. Here is a short Codesnippet to make it a bit clearer:
use Data::Dumper;
my $hash->{$_} = 'abc' foreach (1..4);
print Dumper…
user1558455
1
vote
4 answers
Ruby Autovivification
I've been trying to use autovivification in ruby to do simple record consolidation on this:
2009-08-21|09:30:01|A1|EGLE|Eagle Bulk Shpg|BUY|6000|5.03
2009-08-21|09:30:35|A2|JOYG|Joy Global Inc|BUY|4000|39.76
2009-08-21|09:30:35|A2|LEAP|Leap…
ennuikiller
- 46,381
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1
vote
2 answers
Perl autovivification with TIEHASH
This is the expected and intuitive behavior of a tied hash to handle $h{a}++:
$ perl -E'
sub DESTROY {}
sub AUTOLOAD { say "$AUTOLOAD @_"; bless {} }
tie %h, main;
$h{a}++;
'
main::TIEHASH main
main::FETCH main=HASH(0x7fb6c982a188)…
creaktive
- 5,193
- 2
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1
vote
3 answers
Hash created by autovivification has extra keys
This is what I have
my %count_words;
while (){
my $line= $_;
chomp $line;
my @words = split (/ /, "$line");
foreach my $word(@words){
$count_words{"$word"}++;
}
}
foreach my $key (%count_words){
print…
Amey
- 8,470
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0
votes
0 answers
Autovivify and attribute like access
How can I make my dict autovivify when I access it like ATTRIBUTE i.e. z.ab
class AttrDict(dict):
def __init__(self, *args, **kwargs):
super(AttrDict, self).__init__(*args, **kwargs)
self.__dict__ = self
def…
sten
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