I worked to access the item in ordered dictionary. d is the ordered dictionary:
print d.items()
Here the output is a pair. I want to access the key and value in this pair.
You can unpack the key, value (a tuple) as below:
for key, value in d.items():
print (key)
print (value)
This works both on python 2 and 3.
From docs:
Return a new view of the dictionary’s items ((key, value)
pairs).
Each "pair" in d.items() is a tuple (ordered, immutable sequence) (key, value). You can "unpack" the values in each tuple into separate names, for example in a for loop:
for key, value in d.items():
Related
My goal is to do the following:
Evaluate the existing dictionary using [key(string), item(int), format] and find the item in the dictionary with highest value in key-value pair.
Output the corresponding item (i.e. key value) with the highest value
For example consider the following code:
emails={}
emails={'abc#abc.org':1, 'bcd#bcd.org':2, 'efg#efg.org':3'}
The output should be, in the above example, ('efg#efg.org', 3)
Thank you for your time.
If you want the max evaluated by value then you can do
>>> max(emails.items(), key=lambda x:x[1])
('efg#efg.org', 3)
This solution finds the key with the maximum value; you can then access the dictionary with that key if you want the (key, value) pair.
>>> k = max(emails, key=emails.get)
>>> (k, emails[k])
('efg#efg.org', 3)
I have the following data structure whereby I would like to extract a given key: value pair by searching for the specific value. Use Case: I need to extract u'LOB_B': u'mcsmsg.example.net' from the dict.
{u'status': u'successful',
u'availableFqdnList': [
{u'LOB_A': u'pcload.us.example.net'},
{u'LOB_B': u'mcsmsg.example.net'},
{u'LOB_B': u'gtxd.example.net'},
{u'LOB_B': u'diamond.example.net'}]}
for key, value in my_dict.values():
if value == 'mcsmsg.example.net':
print("Print key value pairs for available FQDN list")
print key, "=", value
Error = for key, value in my_dict.values():
ValueError: too many values to unpack
I don't think values() is the function you want.
Probably you want items() instead.
If you are using python2, you can using iteritems()
Or for python3, it's items()
They will iter the key, value in the dictionary for you.
dic = {'a':1,'b':2}
for key,value in dic.items():
print(key)
print(value)
it will return
a
1
b
2
As a simple to understand way of getting this done
d = {u'status': u'successful',
u'availableFqdnList': [{u'LOB_A': u'pcload.us.example.net'},
{u'LOB_B': u'mcsmsg.example.net'},
{u'LOB_B': u'gtxd.example.net'},
{u'LOB_B': u'diamond.example.net'}]}
for val in d['availableFqdnList']:
if val.values()[0] == "mcsmsg.example.net":
print("%s=%s" %(val.keys()[0], val.values()[0]))
Let's say I have the following code:
my_dict = {str(n*100): n for n in range(5)}
for index, key_value in enumerate(my_dict.items()):
print(index, key_value[0], key_value[1])
Which would create a dictionary with 5 keys and then print (index, key, value) for each key-value pair in the dictionary.
Is there a more elegant way to unpack the dictionary items so that I could do something like:
for index, key, value in unpack_index_and_items(my_dict):
print(index, key, value)
Preferably I'm looking for a one-line replacement for the unpack_index_and_items placeholder and not an actual function.
You are almost there. Just use this:
for index, (k, val) in enumerate(my_dict.items()):
print(index, k, val)
Note the parenthesis around k, val. Without it you get ValueError: need more than 2 values to unpack. The reason is items() returns a (key, value) pair. Look here. Without parenthesis, the tuple returned by items() gets assigned to k, and there is nothing to assign to val, which is why you get the error need more than 2 values to unpack. However, with the parenthesis, the tuple returned by items() is assigned to the tuple (k, val).
I renamed the variables to k and val to distinguish between (key, value) pair returned by items() and the variable names in this example.
Edit: Read about tuple assignment here. Also PEP 3132: Extended Iterable Unpacking
Sure, you can do this:
for index, (key, value) in enumerate(my_dict.items()):
print index, key, value
When we iterate over the dictionary below, each iteration returns(correctly) a key,value pair
for key, value in dict.items():
print "%s key has the value %s" % (key, value)
'some key' key has the value 'some value' (repeated however many times there are a k,v pair)
The above makes sense to me, however if we do this:
for key in dict.items():
print "%s key has the value %s" % (key, value)
("some key", "some value") has the value "some value" (the left tuple will iterate through each key value pair and the right value will just stay at the first value in the dict and repeat)
We end up getting each k,v pair returned in the first %s (key) and the 2nd %s (value) does not iterate, it just returns the first value in the dict for each iteration of the for loop.
I understand that if you iterate with only for key in dict then you are iterating over the keys only. Here since we are iterating a set of tuples (by using dict.items()) with only the key in the for loop, the loop should run for the same number of times as the first example, since there are as many keys as key,value pairs.
What I'm having trouble grasping is why python gives you the entire tuple in the second example for key.
Thanks for the help all -- I'd like to add one more question to the mix.
for a,a in dict.items():
print a
Why does the above print the value, and if i print a,a - obviously both values are printed twice. If I had typed for a,b I would be iterating (key,value) pairs so I would logically think I am now iterating over (key,key) pairs and would therefore print key rather than value. Sorry for the basic questions just playing around in interpreter and trying to figure stuff out.
The first example is utilizing something known as "tuple unpacking" to break what is REALLY the same tuple as in your separate example down into two different variables.
In other words this:
for key, value in dict.items():
Is just this:
for keyvalue in dict.items():
key, value = keyvalue[0], keyvalue[1]
Remember that a for loop always iterates over the individual elements of the iterator you give it. dict.items() returns a list-like object of tuples, so every run through the for loop is a new tuple, automatically unpacked into key, value if you define it as such in the for loop.
It may help to think of it this way:
d = {'a':1, 'b':2, 'c':3}
list(d) # ['a', 'b', 'c'] the keys
list(d.keys()) # ['a', 'b', 'c'] the keys
list(d.values()) # [1, 2, 3] the values
list(d.items()) # [('a',1), ('b',2), ('c',3)] a tuple of (key, value)
N.B. that the only reason your code
for key in dict.items():
print "%s key has value: %s" % (key, value)
Does not throw a NameError is because value is already defined from elsewhere in your code. Since you do not define value anywhere in that for loop, it would otherwise throw an exception.
In the second example you gave you are not assigning "value" to anything:
Notice the small edit here:
for key in dict: ##Removed call to items() because we just want the key,
##Not the key, value pair
value = dict[key] # Added this line
print "%s key has the value %s (key, value)
Note:
In the second example, you could now call dict.keys() or just dict (referencing a dictionary in a for loop will return it's keys). Calling dict.items() will confusingly assign
key=(, )
which is probably not what you want.
How to get a particular key from dictionary in python?
I have a dictionary as :
dict = {'redorange':'1', 'blackhawak':'2', 'garlicbread':'3'}
I want to get value of that key which contains garlic in its key name.
How I can achieve it?
Let's call your dictionary d:
print [v for k,v in d.iteritems() if 'garlic' in k]
prints a list of all corresponding values:
['3']
If you know you want a single value:
print next(v for k,v in d.iteritems() if 'garlic' in k)
prints
'3'
This raises StopIterationError if no such key/value is found. Add the default value:
print next((v for k,v in d.iteritems() if 'garlic' in k), None)
to get None if such a key is not found (or use another default value).