Retain all entries except for one key python
Question:
I have a python dictionary. Just to give out context, I am trying to write my own simple cross validation unit.
So basically what I want is to get all the values except for the given keys.
And depending on the input, it returns all the values from a dictionary except to those what has been given.
So if the input is 2 and 5 then the output values doesn’t have the values from the keys 2 and 5?
Answers:
for key, value in your_dict.items():
if key not in your_blacklisted_set:
print value
the beauty is that this pseudocode example is valid python code.
it can also be expressed as a list comprehension:
resultset = [value for key, value in your_dict.items() if key not in your_blacklisted_set]
How about something along the following lines:
In [7]: d = dict((i,i+100) for i in xrange(10))
In [8]: d
Out[8]:
{0: 100,
1: 101,
2: 102,
3: 103,
4: 104,
5: 105,
6: 106,
7: 107,
8: 108,
9: 109}
In [9]: exc = set((2, 5))
In [10]: for k, v in d.items():
....: if k not in exc:
....: print v
....:
....:
100
101
103
104
106
107
108
109
Also, as a list comprehension using sets:
d = dict(zip(range(9),"abcdefghi"))
blacklisted = [2,5]
outputs = [d[k] for k in set(d.keys())-set(blacklisted)]
Given a dictionary say
d = {
2: 2, 5: 16, 6: 5,
7: 6, 11: 17, 12: 9,
15: 18, 16: 1, 18: 16,
19: 17, 20: 10
}
then the simple comprehension example would attain what you possibly desire
[v for k,v in d.iteritems() if k not in (2,5)]
This example lists all values not with keys {2,5}
for example the O/P of the above comprehension is
[5, 6, 1, 17, 9, 18, 1, 16, 17, 10]
Just for fun with sets
keys = set(d.keys())
excludes = set([...])
for key in keys.difference(excludes):
print d[key]
keys = ['a', 'b']
a_dict = {'a':1, 'b':2, 'c':3, 'd':4}
[a_dict.pop(key) for key in keys]
After popping out the keys to be discarded, a_dict will retain the ones you’re after.
If your goal is to return a new dictionary, with all key/values except one or a few, use the following:
exclude_keys = ['exclude', 'exclude2']
new_d = {k: d[k] for k in set(list(d.keys())) - set(exclude_keys)}
where 'exclude' can be replaced by (a list of) key(s) which should be excluded.
using exception handling
facebook_posts = [
{'Likes': 21, 'Comments': 2},
{'Likes': 13, 'Comments': 2, 'Shares': 1},
{'Likes': 33, 'Comments': 8, 'Shares': 3},
{'Comments': 4, 'Shares': 2},
{'Comments': 1, 'Shares': 1},
{'Likes': 19, 'Comments': 3}
]
total_likes = 0
for post in facebook_posts:
try:
total_likes = total_likes + post['Likes']
except KeyError:
pass
print(total_likes)
you can also use:
except KeyError: 'My Key'
but probably only good for once off use
Be careful of using a shallow copy if you intend to modify the resulting dict.
import copy
def copy_dict_except_keys_shallow(d:dict, exclude_keys):
return {k: d[k] for k in set(list(d.keys())) - set(exclude_keys)}
def copy_dict_except_keys_deep(d:dict, exclude_keys):
return {k: copy.deepcopy(d[k]) for k in set(list(d.keys())) - set(exclude_keys)}
original = {'a': 1, 'b': [1, 2, 3]}
deep = copy_dict_except_keys_deep(original, ['a'])
deep['b'].append(4)
print("Modifying the deep copy preserves the original")
print(f"original: {original}")
print(f"deep copy: {deep}")
print()
shallow = copy_dict_except_keys_shallow(original, 'a')
shallow['b'].append(4)
print("Modifying the shallow copy changes the original")
print(f"original: {original}")
print(f"shallow copy: {shallow}")
Modifying the deep copy preserves the original
original: {'a': 1, 'b': [1, 2, 3]}
deep copy: {'b': [1, 2, 3, 4]}
Modifying the shallow copy changes the original
original: {'a': 1, 'b': [1, 2, 3, 4]}
shallow copy: {'b': [1, 2, 3, 4]}
I have a python dictionary. Just to give out context, I am trying to write my own simple cross validation unit.
So basically what I want is to get all the values except for the given keys.
And depending on the input, it returns all the values from a dictionary except to those what has been given.
So if the input is 2 and 5 then the output values doesn’t have the values from the keys 2 and 5?
for key, value in your_dict.items():
if key not in your_blacklisted_set:
print value
the beauty is that this pseudocode example is valid python code.
it can also be expressed as a list comprehension:
resultset = [value for key, value in your_dict.items() if key not in your_blacklisted_set]
How about something along the following lines:
In [7]: d = dict((i,i+100) for i in xrange(10))
In [8]: d
Out[8]:
{0: 100,
1: 101,
2: 102,
3: 103,
4: 104,
5: 105,
6: 106,
7: 107,
8: 108,
9: 109}
In [9]: exc = set((2, 5))
In [10]: for k, v in d.items():
....: if k not in exc:
....: print v
....:
....:
100
101
103
104
106
107
108
109
Also, as a list comprehension using sets:
d = dict(zip(range(9),"abcdefghi"))
blacklisted = [2,5]
outputs = [d[k] for k in set(d.keys())-set(blacklisted)]
Given a dictionary say
d = {
2: 2, 5: 16, 6: 5,
7: 6, 11: 17, 12: 9,
15: 18, 16: 1, 18: 16,
19: 17, 20: 10
}
then the simple comprehension example would attain what you possibly desire
[v for k,v in d.iteritems() if k not in (2,5)]
This example lists all values not with keys {2,5}
for example the O/P of the above comprehension is
[5, 6, 1, 17, 9, 18, 1, 16, 17, 10]
Just for fun with sets
keys = set(d.keys())
excludes = set([...])
for key in keys.difference(excludes):
print d[key]
keys = ['a', 'b']
a_dict = {'a':1, 'b':2, 'c':3, 'd':4}
[a_dict.pop(key) for key in keys]
After popping out the keys to be discarded, a_dict will retain the ones you’re after.
If your goal is to return a new dictionary, with all key/values except one or a few, use the following:
exclude_keys = ['exclude', 'exclude2']
new_d = {k: d[k] for k in set(list(d.keys())) - set(exclude_keys)}
where 'exclude' can be replaced by (a list of) key(s) which should be excluded.
using exception handling
facebook_posts = [
{'Likes': 21, 'Comments': 2},
{'Likes': 13, 'Comments': 2, 'Shares': 1},
{'Likes': 33, 'Comments': 8, 'Shares': 3},
{'Comments': 4, 'Shares': 2},
{'Comments': 1, 'Shares': 1},
{'Likes': 19, 'Comments': 3}
]
total_likes = 0
for post in facebook_posts:
try:
total_likes = total_likes + post['Likes']
except KeyError:
pass
print(total_likes)
you can also use:
except KeyError: 'My Key'
but probably only good for once off use
Be careful of using a shallow copy if you intend to modify the resulting dict.
import copy
def copy_dict_except_keys_shallow(d:dict, exclude_keys):
return {k: d[k] for k in set(list(d.keys())) - set(exclude_keys)}
def copy_dict_except_keys_deep(d:dict, exclude_keys):
return {k: copy.deepcopy(d[k]) for k in set(list(d.keys())) - set(exclude_keys)}
original = {'a': 1, 'b': [1, 2, 3]}
deep = copy_dict_except_keys_deep(original, ['a'])
deep['b'].append(4)
print("Modifying the deep copy preserves the original")
print(f"original: {original}")
print(f"deep copy: {deep}")
print()
shallow = copy_dict_except_keys_shallow(original, 'a')
shallow['b'].append(4)
print("Modifying the shallow copy changes the original")
print(f"original: {original}")
print(f"shallow copy: {shallow}")
Modifying the deep copy preserves the original
original: {'a': 1, 'b': [1, 2, 3]}
deep copy: {'b': [1, 2, 3, 4]}
Modifying the shallow copy changes the original
original: {'a': 1, 'b': [1, 2, 3, 4]}
shallow copy: {'b': [1, 2, 3, 4]}