Imagine I have a dictionary like this:
d = {'1':['a'], '2':['b', 'c', 'd'], '3':['e', 'f'], '4':['g']}
Each key of the dictionary represents a unique person of a certain class.
Each key must have only one value.
Key's with one value represent the correct reassignment.
Key's with more than one value represent the possibilities. One of those values is the most correct for that key.
I have a processed list with the most correct value.
LIST = ['c', 'e']
I must now iterate values of LIST through values of dictionary when len(values) > 1 and replace them to look like this:
d = {'1':['a'], '2':['c'], '3':['e'], '4':['g']}
Initialise your correct values inside a set.
correct = {'c', 'e'}
# correct = set(LIST)
Now, assuming list values with more than one element can have only a single correct element, you can build a dictionary using a conditional comprehension:
d2 = {k : list(correct.intersection(v)) if len(v) > 1 else v for k, v in d.items()}
print(d2)
# {'1': ['a'], '2': ['c'], '3': ['e'], '4': ['g']}
If there can be more than one possible correct value, you can take just the first one.
d2 = {}
for k, v in d.items():
if len(v) > 1:
c = list(correct.intersection(v))
v = c[:1]
d2[k] = v
print(d2)
# {'1': ['a'], '2': ['c'], '3': ['e'], '4': ['g']}
If you meant to mutate d in-place (because making a full copy can be expensive), then the above solution simplifies to
for k, v in d.items():
if len(v) > 1:
c = list(correct.intersection(v))
d[k] = c[:1]
print(d)
# {'1': ['a'], '2': ['c'], '3': ['e'], '4': ['g']}
Another approach in one statement using dict comprehension:
d = {'1':['a'], '2':['b', 'c', 'd'], '3':['e', 'f'], '4':['g']}
a = ['c', 'e']
output = {k: v if not any(j in set(a) for j in v) else list(set(v) & set(a)) if v and isinstance(v, (list, tuple)) else [] for k, v in d.items()}
# More readeable like this:
# {
# k: v if not any(j in set(a) for j in v) else list(set(v) & set(a))
# if v and isinstance(v, (list, tuple))
# else [] for k, v in d.items()
# }
print(output)
Output:
{'1': ['a'], '2': ['c'], '3': ['e'], '4': ['g']}
Related
Take this for example:
d = {1: ['a', 'b', 'c'], 2: ['d', 'e', 'f'], 3: [1, 'i', 'j']}
I want to check if a value x exists inside of any of the lists in the dictionary, if it does, return the key of the list it's in.
So checking if 1 was in any of the lists in d, would return 3 (the key).
I know how to do this in the case that the dictionary values are not an iterable, but I'm having trouble figuring out how to do it when it is an iterable.
You can use list comprehension.
d = {1: ['a', 'b', 'c'], 2: ['d', 'e', 'f'], 3: [1, 'i', 'j']}
def ret_key_base_val(dct, val):
return [k for k,v in dct.items() if val in v]
result = ret_key_base_val(d, 1)
print(result)
# [3]
Using a list comprehension:
filtered_d = [k for k,v in d.items() if 1 in v]
for k, v for d.items() is your friend here, it will allow you easy access to both key and values in the context of your for-loop.
To support multiple types for v (making comprehensions tough to read/follow), then use type(v) and some if statements.
This question already has answers here:
Reverse / invert a dictionary mapping
(32 answers)
Closed 10 months ago.
I have a dictionary as follows:
d = {'a': ['b'], 'c': ['d']}
I want to change the positions of the dictionary so that it looks like the following:
d_new = {'b': 'a', 'd': 'c'}
I have tried the following, but due to the second term being a list in my original dictionary (d), I am unable to complete this.
d = {'a': ['b'], 'c': ['d']}
for k in list(d.keys()):
d[d.pop(k)] = k
print(d)
You can use iterable unpacking in a dict comprehension like so:
{v: k for k, (v,) in d.items()}
>>> d = {'a': ['b'], 'c': ['d']}
>>> {v: k for k, (v,) in d.items()}
{'b': 'a', 'd': 'c'}
This assumes all values are a list of one element and you only want the first element in the lists.
Otherwise you can use this more appropriate code:
{v[0] if isinstance(v, list) else v: k for k, v in d.items()}
A variation on a theme using list unpacking:
d = {'a': ['b'], 'c': ['d']}
d = {v: k for k, [v] in d.items()}
print(d)
In case the values (lists) happen to contain more than one element and you're only interested in the first element then:
d = {v:k for k, [v,*_] in d.items()}
Of course, this could also be used even if there's only one element per list
I need to combine two dictionaries by their value, resulting in a new key which is the list of keys with the shared value. All I can find online is how to add two values with the same key or how to simply combine two dictionaries, so perhaps I am just searching in the wrong places.
To give an idea:
dic1 = {'A': 'B', 'C': 'D'}
dic2 = {'D': 'B', 'E': 'F'}
Should result in:
dic3 = {['A', 'D']: 'B', 'C': 'D', 'E': 'F'}
I am not sure why you would need such a data structure, you can probably find a better solution to your problem. However, just for the sake of answering your question, here is a possible solution:
dic1 = {'A':'B', 'C':'D'}
dic2 = {'D':'B', 'E':'F'}
key_list = list(dic2.keys())
val_list = list(dic2.values())
r = {}
for k,v in dic1.items():
if v in val_list:
i = val_list.index(v) #get index at value
k2 = key_list[i] #use index to retrive the key at value
r[(k, k2)] = v #make the dict entry
else:
r[k] = v
val_list = list(r.values()) #get all the values already processed
for k,v in dic2.items():
if v not in val_list: #if missing value
r[k] = v #add new entry
print(r)
output:
{('A', 'D'): 'B', 'C': 'D', 'E': 'F'}
You can't assign a list as a key in a python dictionary since the key must be hashable and a list is not an ashable object, so I have used a tuple instead.
I would use a defaultdict of lists and build a reversed dict and in the end reverse it while converting the lists to tuples (because lists are not hashable and can't be used as dict keys):
from collections import defaultdict
dic1 = {'A':'B', 'C':'D'}
dic2 = {'D':'B', 'E':'F'}
temp = defaultdict(list)
for d in (dic1, dic2):
for key, value in d.items():
temp[value].append(key)
print(temp)
res = {}
for key, value in temp.items():
if len(value) == 1:
res[value[0]] = key
else:
res[tuple(value)] = key
print(res)
The printout from this (showing the middle step of temp) is:
defaultdict(<class 'list'>, {'B': ['A', 'D'], 'D': ['C'], 'F': ['E']})
{('A', 'D'): 'B', 'C': 'D', 'E': 'F'}
If you are willing to compromise from 1-element tuples as keys, the second part will become much simpler:
res = {tuple(value): key for key, value in temp.items()}
I made a mistake in my question here (wrong requested input and expected output):
Comparing dicts, updating NOT overwriting values
I am not looking for this solution:
Combining 2 dictionaries with common key
So this question is not a duplicate
Problem statement:
requested input:
d1 = {'a': ['a'], 'b': ['b', 'c']}
d2 = {'b': ['c', 'd'], 'c': ['e','f']}
expected output (I don't care about the order of the keys / values!):
new_dict = {'a': ['a'], 'b': ['b', 'c', 'd'], 'c': ['e', 'f']}
The solution in Combining 2 dictionaries with common key
gives following output:
new_dict = {'a': ['a'], 'b': ['b', 'c', 'c', 'd'], 'c': ['e', 'f']}
I don't want the duplicates to be stored.
My solution (it works but it is not so efficient):
unique_vals = []
new_dict = {}
for key in list(d1.keys())+list(d2.keys()) :
unique_vals = []
try:
for val in d1[key]:
try:
for val1 in d2[key]:
if(val1 == val) and (val1 not in unique_vals):
unique_vals.append(val)
except:
continue
except:
new_dict[key] = unique_vals
new_dict[key] = unique_vals
for key in d1.keys():
for val in d1[key]:
if val not in new_dict[key]:
new_dict[key].append(val)
for key in d2.keys():
for val in d2[key]:
if val not in new_dict[key]:
new_dict[key].append(val)
Here is how I would go about it:
d1 = {'a': ['a'], 'b': ['b', 'c']}
d2 = {'b': ['c', 'd'], 'c': ['e','f']}
dd1 = {**d1, **d2}
dd2 = {**d2, **d1}
{k:list(set(dd1[k]).union(set(dd2[k]))) for k in dd1}
Produces the desired result.
I suggest using a default dictionary collection with a set as a default value.
It guarantees that all values will be unique and makes the code cleaner.
Talking about efficiecy it's O(n^2) by time.
from collections import defaultdict
d1 = {'a': ['a'], 'b': ['b', 'c']}
d2 = {'b': ['c', 'd'], 'c': ['e','f']}
new_dict = defaultdict(set)
for k, v in d1.items():
new_dict[k] = new_dict[k].union(set(v))
for k, v in d2.items():
new_dict[k] = new_dict[k].union(set(v))
Try this code. You can remove deep copy if modifications in the initial array are fine for you.
import copy
def merge(left, right):
res = copy.deepcopy(left)
for k, v in right.items():
res[k] = list(set(res[k]).union(v)) if k in res else v
return res
Simple if statement if you don't want to use a Set.
d3 = dict(d2)
for k,v in d1.items():
if k not in d3:
d3[k] = v
else:
for n in d1[k]:
if n not in d3[k]:
d3[k].append(n)
Sorry about the question repost...I should have just edited this question in the first place. Flagged the new one for the mods. Sorry for the trouble
Had to re-write the question due to changed requirements.
I have a dictionary such as the following:
d = {'a': [4, 2], 'b': [3, 4], 'c': [4, 3], 'd': [4, 3], 'e': [4], 'f': [4], 'g': [4]}
I want to get the keys that are associated with the smallest length in the dictionary d, as well as those that have the maximum value.
In this case, the keys with the smallest length (smallest length of lists in this dictionary) should return
'e, 'f', 'g'
And those with the greatest value(the sum of the integers in each list) should return
'b' 'c'
I have tried
min_value = min(dict.itervalues())
min_keys = [k for k in d if dict[k] == min_value]
But that does not give me the result I want.
Any ideas?
Thanks!
Your problem is that your lists contain strings ('2'), and not integers (2). Leave out the quotes, or use the following:
min_value = min(min(map(int, v) for v in dct.values()))
min_keys = [k for k,v in d.items() if min_value in map(int, v)]
Similarily, to calculate the keys with the max length:
max_length = max(map(len, dct.values()))
maxlen_keys = [k for k,v in d.items() if max_length == len(v)]
Also, it's a bad idea to use dict as a variable name, as doing so overshadows the built-in dict.
You can use min() with a key= argument, and specify a key function that compares the way you want.
d = {'a': ['1'], 'b': ['1', '2'], 'c': ['2'], 'd':['1']}
min_value = min(d.values())
min_list = [key for key, value in d.items() if value == min_value]
max_len = len(max(d.values(), key=len))
long_list = [key for key, value in d.items() if len(value) == max_len]
print(min_list)
print(long_list)
Notes:
0) Don't use dict as a variable name; that's the name of the class for dictionary, and if you use it as a variable name you "shadow" it. I just used d for the name here.
1) min_value was easy; no need to use a key= function.
2) max_len uses a key= function, len(), to find the longest value.
How about using sorting and lambdas?
#!/usr/bin/env python
d = {'a': ['1'], 'b': ['1', '2'], 'c': ['8', '1'], 'd':['1'], 'e':['1', '2', '3'], 'f': [4, 1]}
sorted_by_sum_d = sorted(d, key=lambda key: sum(list(int(item) for item in d[key])))
sorted_by_length_d = sorted(d, key=lambda key: len(d[key]))
print "Sorted by sum of the items in the list : %s" % sorted_by_sum_d
print "Sorted by length of the items in the list : %s" % sorted_by_length_d
This would output:
Sorted by sum of the items in the list : ['a', 'd', 'b', 'f', 'e', 'c']
Sorted by length of the items in the list : ['a', 'd', 'c', 'b', 'f', 'e']
Be aware I changed the initial 'd' dictionary (just to make sure it was working)
Then, if you want the item with the biggest sum, you get the last element of the sorted_by_sum_d list.
(I'm not too sure this is what you want, though)
Edit:
If you can ensure that the lists are always going to be lists of integers (or numeric types, for that matter, such as long, float...), there's not need to cast strings to integers. The calculation of the sorted_by_sum_d variable can be done simply using:
d = {'a': [1], 'b': [1, 2], 'c': [8, 1], 'd':[1], 'e':[1, 2, 3], 'f': [4, 1]}
sorted_by_sum_d = sorted(d, key=lambda key: sum(d[key]))
I've found such a simple solution:
min_len = len(min(d.values(), key=(lambda value: len(value)))) # 1
min_keys = [key for i, key in enumerate(d) if len(d[key]) == min_len] # ['e', 'f', 'g']