List match

[OriginalBrownster]

Hi there:

I know this probably is a very easy thing to do in python, but i wanted
to compare 2 lists and generate a new list that does not copy similar
entries. An example below

list= ["apple", "banana", "grape"]
list2=["orange","banana", "pear"]

now I want to compare these lits and generate a third list after
comparison

list3 would be ["apple", "banana","grape","orange", "pear"]

hence the double entry would not show up?

Is there a way to do this??

Stephen

[Richie Hindle]

[Stephen]

[...] compare 2 lists and generate a new list that does not copy similar
entries. An example below

list= ["apple", "banana", "grape"]
list2=["orange","banana", "pear"]

now I want to compare these lits and generate a third list after
comparison

list3 would be ["apple", "banana","grape","orange", "pear"]

Use sets:

>>from sets import Set as set # For compatibility with Python 2.3
one = ["apple", "banana", "grape"]
two = ["orange","banana", "pear"]
print list(set(one) | set(two))

['grape', 'apple', 'orange', 'pear', 'banana']

--
Richie Hindle
ri****@entrian.com

[thunderfoot]

OriginalBrownster wrote:

Hi there:

I know this probably is a very easy thing to do in python, but i wanted
to compare 2 lists and generate a new list that does not copy similar
entries. An example below

list= ["apple", "banana", "grape"]
list2=["orange","banana", "pear"]

now I want to compare these lits and generate a third list after
comparison

list3 would be ["apple", "banana","grape","orange", "pear"]

hence the double entry would not show up?

Is there a way to do this??

Stephen

How about:

list3 = list1 + [item for item in list2 if item not in list1]

print list3:

['apple', 'banana', 'grape', 'orange', 'pear']

[thunderfoot]

OriginalBrownster wrote:

Hi there:

I know this probably is a very easy thing to do in python, but i wanted
to compare 2 lists and generate a new list that does not copy similar
entries. An example below

list= ["apple", "banana", "grape"]
list2=["orange","banana", "pear"]

now I want to compare these lits and generate a third list after
comparison

list3 would be ["apple", "banana","grape","orange", "pear"]

hence the double entry would not show up?

Is there a way to do this??

Stephen

How about:

list3 = list1 + [item for item in list2 if item not in list1]

print list3:

['apple', 'banana', 'grape', 'orange', 'pear']

[Richard Brodie]

"OriginalBrownster" <or***************@gmail.comwrote in message
news:11********************@74g2000cwt.googlegroup s.com...

I know this probably is a very easy thing to do in python, but i wanted
to compare 2 lists and generate a new list that does not copy similar
entries. An example below

list= ["apple", "banana", "grape"]
list2=["orange","banana", "pear"]

Other people have already posted solutions but I'll add a couple of
comments:

1. Avoid calling lists 'list', you will break the list built-in function.

2. You don't specify whether the lists are ordered. If there is no
significance to the order of the items, it may be more appropriate
to use sets throughout. Then the answer is just: set3 = set1 | set2.

[Stargaming]

Richie Hindle schrieb:

[Stephen]

>>[...] compare 2 lists and generate a new list that does not copy similar
entries. An example below

list= ["apple", "banana", "grape"]
list2=["orange","banana", "pear"]

now I want to compare these lits and generate a third list after
comparison

list3 would be ["apple", "banana","grape","orange", "pear"]

Use sets:

>>>>from sets import Set as set # For compatibility with Python 2.3
one = ["apple", "banana", "grape"]
two = ["orange","banana", "pear"]
print list(set(one) | set(two))

['grape', 'apple', 'orange', 'pear', 'banana']

Why using Set two times, when you can do it with one call?

>>list(set(one + two))

According to my benchmarks, this was five times faster than calling it
twice and use |.

There are also a few more good approaches uniquifying lists at
http://www.peterbe.com/plog/uniqifiers-benchmark

Regards,
Stargaming

[Paddy]

th*********@gmail.com wrote:

OriginalBrownster wrote:

Hi there:

I know this probably is a very easy thing to do in python, but i wanted
to compare 2 lists and generate a new list that does not copy similar
entries. An example below

list= ["apple", "banana", "grape"]
list2=["orange","banana", "pear"]

now I want to compare these lits and generate a third list after
comparison

list3 would be ["apple", "banana","grape","orange", "pear"]

hence the double entry would not show up?

Is there a way to do this??

Stephen

How about:

list3 = list1 + [item for item in list2 if item not in list1]

print list3:

['apple', 'banana', 'grape', 'orange', 'pear']

It works with the data given, but if list1 contains duplicates...

- Pad

[Paddy]

OriginalBrownster wrote:

Hi there:

I know this probably is a very easy thing to do in python, but i wanted
to compare 2 lists and generate a new list that does not copy similar
entries. An example below

list= ["apple", "banana", "grape"]
list2=["orange","banana", "pear"]

now I want to compare these lits and generate a third list after
comparison

list3 would be ["apple", "banana","grape","orange", "pear"]

hence the double entry would not show up?

Is there a way to do this??

Stephen

This solution uses sets; removes all duplicates and is order
preserving.
Remove the outer sorted wrapper if the order need not be preserved.

>>lst= ["apple", "banana", "grape"]
lst2=["orange","banana", "pear"]
lst3= lst+lst2
sorted([x for x in set(lst3)], key = lambda x: lst3.index(x))

['apple', 'banana', 'grape', 'orange', 'pear']

>>>

- Paddy