appending to dict

[bucket79]

Hi
is there anyway appending to dictionary?
list has this feature

a = []
a.append(1)
print a

[1]

but dictionary can't
i wanna do like this thing{1:2, 3:4}

so i try this feature likebut this make's error
because a.keys().append(3) makes 'None' (i can't understand this )

so i try copy.copy(a.values()).append(4)))
and
a = dict(zip(copy.deepcopy(a.keys()).append(3),
copy.deepcopy(a.values()).append(4)))
but this make's error, too

why a.keys().append(3) makes 'None' ?
and is there anyway appending to dictionary?

any post will be appreciated

 

[Hugh Macdonald]

On 14 May 2004 02:40:00 -0700

Hi
is there anyway appending to dictionary?
list has this feature

a = []
a.append(1)
print a

[1]

but dictionary can't
i wanna do like this thing{1:2, 3:4}

a = {1:2}
a.update({3:4})

 

[=?ISO-8859-1?Q?Holger_T=FCrk?=]

why a.keys().append(3) makes 'None' ?

Because .append modifies the list in place. It does
not return a new list.

and is there anyway appending to dictionary?

key/value pairs in a dictionary are not ordered. There
is no "last pair". So you can't append to a dictionary.
But you can update it with another dictionary.
Use something like: adict.update (anotherdict)

keys () returns a list of keys in the dictionary.
The order of the elements in this list is arbitrary
(or somehow ordered afterwards). But there is no
real list of keys in the dictionary itself.

Greetings,

Holger

 

[Peter Hansen]

is there anyway appending to dictionary?
list has this feature

a = []
a.append(1)
print a

[1]

but dictionary can't
i wanna do like this thing
{1:2, 3:4}

Did you know that the following actually works?

>>> a = {1: 2} # note: your syntax was wrong here
>>> print a {1: 2}
>>> a[3] = 4
>>> print a

{1: 2, 3: 4}

Since, as Holger pointed out, dictionaries aren't ordered,
the concept implicit in "append" doesn't apply. The more
appropriate concept "update", however, can be spelled either
dict.update(), or like what I just showed, for dictionaries.

-Peter

 

[Heather Coppersmith]

On 14 May 2004 02:40:00 -0700,

is there anyway appending to dictionary?
list has this feature

a = []
a.append(1)
print a

[1]

but dictionary can't
i wanna do like this thing{1:2, 3:4}

Maybe I'm missing something. Try this:

a = { 1:2 }
a[ 3 ] = 4

and then check out

http://www.python.org/doc/current/tut/node7.html#SECTION007400000000000000000

and

http://www.python.org/doc/current/lib/typesmapping.html

HTH,
Heather