Idiomatic Python to convert list to dict

[James Fassett]

Hi all,

Simple question really on a best practice. I want to avoid adding
duplicates to a list.

my_list = ['a', 'b', 'c', 'd', 'e']
dup_map = {}
for item in my_list:
dup_map[item] = True

# ... sometime later

for complex_dict in large_list:
if complex_dict["char"] not in dup_map:
my_list.append( complex_dict["char"])
dup_map[complex_dict["char"]] = True

For the first part (generating the duplicate map) is there a more
idiomatic Python method for flipping the list into a dict?

Is there a better way to achieve the overall objective (as hinted at
by the above algorithm)?

Thanks in advance for any tips.

James.

[Diez B. Roggisch]

Re: Idiomatic Python to convert list to dict

James Fassett schrieb:

Hi all,
>
Simple question really on a best practice. I want to avoid adding
duplicates to a list.
>
my_list = ['a', 'b', 'c', 'd', 'e']
dup_map = {}
for item in my_list:
dup_map[item] = True
>
# ... sometime later
>
for complex_dict in large_list:
if complex_dict["char"] not in dup_map:
my_list.append( complex_dict["char"])
dup_map[complex_dict["char"]] = True
>
For the first part (generating the duplicate map) is there a more
idiomatic Python method for flipping the list into a dict?
>
Is there a better way to achieve the overall objective (as hinted at
by the above algorithm)?
>
Thanks in advance for any tips.

Instead of a dict, use a set. It's immediatly contructable from my_list,
and better suited for the task anyway.

Diez

[craig75]

Re: Idiomatic Python to convert list to dict

On Jul 10, 10:06 am, James Fassett <ja...@reggieba nd.comwrote:

Hi all,
>
Simple question really on a best practice. I want to avoid adding
duplicates to a list.
>
my_list = ['a', 'b', 'c', 'd', 'e']
dup_map = {}
for item in my_list:
    dup_map[item] = True
>
# ... sometime later
>
for complex_dict in large_list:
    if complex_dict["char"] not in dup_map:
        my_list.append( complex_dict["char"])
        dup_map[complex_dict["char"]] = True
>
For the first part (generating the duplicate map) is there a more
idiomatic Python method for flipping the list into a dict?
>
Is there a better way to achieve the overall objective (as hinted at
by the above algorithm)?
>
Thanks in advance for any tips.
>
James.

The dictionary seems like overkill here because, if I understand
correctly, the only value associated with a key is "True". So in that
case just remove all the code related to the dictionary (and
complex_dict) and you end up with

my_list = ['a', 'b', 'c', 'd', 'e']

# ... sometime later
for char in large_list:
if char not in my_list:
my_list.append( char)


However, as Diez suggests, use a set:

my_list = set(['a', 'b', 'c', 'd', 'e'])
# ... sometime later
for char in large_list:
my_list.add(cha r) # will not add duplicates

[James Fassett]

Re: Idiomatic Python to convert list to dict

On Jul 10, 6:13 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

my_list = ['a', 'b', 'c', 'd', 'e']
dup_map = {}
for item in my_list:
    dup_map[item] = True

>

# ... sometime later

>

for complex_dict in large_list:
    if complex_dict["char"] not in dup_map:
        my_list.append( complex_dict["char"])
        dup_map[complex_dict["char"]] = True

>
Instead of a dict, use a set. It's immediatly contructable from my_list,
and better suited for the task anyway.

Cheers,

I rewrote it similar to:

dup_map = set(['a', 'b', 'c', 'd', 'e'])

# ... sometime later

for complex_dict in large_list:
dup_map.add(com plex_dict["char"])

my_list = list(dup_map)

That is a little nicer. Thanks again,
James.