迭代和比较Python中的列表列表

Question

I have 2 lists in Python:

checkNameArr = [['551002', 'Derek Jones'], 
                ['940874', 'Hugh Lunny'], 
                ['104741', 'Richard Plaith'], 
                ['310125', 'Aideen Toner'], 
                ['305795', 'Vikki Trench'], 
                ['218714', 'Paul Cutland'], 
                ['401741', 'Russell Smith'], 
                ['223996', 'Chloe Green'], 
                ['845216', 'Simon Fallon'], 
                ['402258', 'Chris Worth']]

queryNameArr = [['551002', 'Derek Jones'], 
                ['940874', 'Hugh Lunny'], 
                ['823085', 'Brian Deans'], 
                ['310125', 'Aideen Toner'], 
                ['571454', 'Pam Scales'], 
                ['967825', 'Una Lingus'], 
                ['401741', 'Russell Smith'], 
                ['682301', 'Hannah Jacobs'], 
                ['914774', 'Elaine Glass'], 
                ['402258', 'Chris Worth']]

And I would like to compare the number value in each list. I know that I would need to iterate through one list to compare it to the first value of the next list, if a match is found, store it in a found list. If it isn't found, store that value in a not found list. I am trying to do this in the smallest amount of code possible but the logistics of this are confusing me.

What would be a nice clean solution?

Answer 1

I would convert the list in which you want to check to set by converting each inner element to tuple and then iterate over the other list and check if its element (converted to tuple) exists in the set, if so add it to found list, else add it to notfound list.

Example -

checkNameSet = set(map(tuple, checkNameArr))
found = []
notfound = []
for i in queryNameArr:
    if tuple(i) in checkNameSet:
        found.append(i)
    else:
        notfound.append(i)

Demo -

>>> checkNameArr = [['551002', 'Derek Jones'],
...                 ['940874', 'Hugh Lunny'],
...                 ['104741', 'Richard Plaith'],
...                 ['310125', 'Aideen Toner'],
...                 ['305795', 'Vikki Trench'],
...                 ['218714', 'Paul Cutland'],
...                 ['401741', 'Russell Smith'],
...                 ['223996', 'Chloe Green'],
...                 ['845216', 'Simon Fallon'],
...                 ['402258', 'Chris Worth']]
>>>
>>> queryNameArr = [['551002', 'Derek Jones'],
...                 ['940874', 'Hugh Lunny'],
...                 ['823085', 'Brian Deans'],
...                 ['310125', 'Aideen Toner'],
...                 ['571454', 'Pam Scales'],
...                 ['967825', 'Una Lingus'],
...                 ['401741', 'Russell Smith'],
...                 ['682301', 'Hannah Jacobs'],
...                 ['914774', 'Elaine Glass'],
...                 ['402258', 'Chris Worth']]
>>>
... checkNameSet = set(map(tuple, checkNameArr))
>>> found = []
>>> notfound = []
>>> for i in queryNameArr:
...     if tuple(i) in checkNameSet:
...             found.append(i)
...     else:
...             notfound.append(i)
...
>>> found
[['551002', 'Derek Jones'], ['940874', 'Hugh Lunny'], ['310125', 'Aideen Toner'], ['401741', 'Russell Smith'], ['402258', 'Chris Worth']]
>>> notfound
[['823085', 'Brian Deans'], ['571454', 'Pam Scales'], ['967825', 'Una Lingus'], ['682301', 'Hannah Jacobs'], ['914774', 'Elaine Glass']]

---

If you only want to compare using one element or a subset of elements of the inner list, instead of storing the complete tuple of inner list in the set, we can use operator.itemgetter() to get just the element to compare and store that alone.

And then compare using that alone , Code -

import operator
checkNameSet = set(map(operator.itemgetter(0), checkNameArr))
found = []
notfound = []
for i in queryNameArr:
    if i[0] in checkNameSet:
        found.append(i)
    else:
        notfound.append(i)

Example/Demo for this -

>>> checkNameArr = [['551002', 'Derek Jones'],
...                 ['940874', 'Hugh Lunny'],
...                 ['104741', 'Richard Plaith'],
...                 ['310125', 'Aideen Toner'],
...                 ['305795', 'Vikki Trench'],
...                 ['218714', 'Paul Cutland'],
...                 ['401741', 'Russell Smith'],
...                 ['223996', 'Chloe Green'],
...                 ['845216', 'Simon Fallon'],
...                 ['402258', 'Chris Worth']]
>>>
>>> queryNameArr = [['551002', 'Derek Jones'],
...                 ['940874', 'Hugh Lunny'],
...                 ['823085', 'Brian Deans'],
...                 ['310125', 'Aideen Toner'],
...                 ['571454', 'Pam Scales'],
...                 ['967825', 'Una Lingus'],
...                 ['401741', 'Russell Smith'],
...                 ['682301', 'Hannah Jacobs'],
...                 ['914774', 'Elaine Glass'],
...                 ['402258', 'Chris Worth']]
>>>
... checkNameSet = set(map(operator.itemgetter(0), checkNameArr))
>>> found = []
>>> notfound = []
>>> for i in queryNameArr:
...     if i[0] in checkNameSet:
...             found.append(i)
...     else:
...             notfound.append(i)
...
>>> found
[['551002', 'Derek Jones'], ['940874', 'Hugh Lunny'], ['310125', 'Aideen Toner'], ['401741', 'Russell Smith'], ['402258', 'Chris Worth']]
>>> notfound
[['823085', 'Brian Deans'], ['571454', 'Pam Scales'], ['967825', 'Una Lingus'], ['682301', 'Hannah Jacobs'], ['914774', 'Elaine Glass']]

Answer 2

matchingArr = [item for item in queryNameArr if item in checkNameArr]
notMatchingArr = [item for item in queryNameArr if not item in checkNameArr]

Result:

[['551002', 'Derek Jones'],
 ['940874', 'Hugh Lunny'],
 ['310125', 'Aideen Toner'],
 ['401741', 'Russell Smith'],
 ['402258', 'Chris Worth']]

[['823085', 'Brian Deans'],
 ['571454', 'Pam Scales'],
 ['967825', 'Una Lingus'],
 ['682301', 'Hannah Jacobs'],
 ['914774', 'Elaine Glass']]

---

An alternative based on sets:

matchingArr = map(list, set(map(tuple, queryNameArr)).intersection(set(map(tuple, checkNameArr))))
notMatchingArr = map(list, set(map(tuple, queryNameArr)).difference(set(map(tuple, checkNameArr))))

The conversion from list to tuple and vice versa is somewhat annoying... (but needed, because sets can't work on lists).

Answer 3

# first, let’s create a set of the check list to quickly check for membership
checkNameSet = set(tuple(x) for x in checkNameArr)

# create lists for matched, and unmatched names
matched = []
unmatched = []

# iterate the query names
for query in queryNameArr:
    # if the query name is in the check set, add it to matched, otherwise unmatched
    if tuple(query) in checkNameSet:
        matched.append(query)
    else:
        unmatched.append(query)

>>> matched
[['551002', 'Derek Jones'], ['940874', 'Hugh Lunny'], ['310125', 'Aideen Toner'], ['401741', 'Russell Smith'], ['402258', 'Chris Worth']]
>>> unmatched
[['823085', 'Brian Deans'], ['571454', 'Pam Scales'], ['967825', 'Una Lingus'], ['682301', 'Hannah Jacobs'], ['914774', 'Elaine Glass']]