I am creating a dictionary of lists using integers as key in python. However the following code gives me t is None.
t = y.get("1",[]).append(1)
(But when I do counter[c] = counter.get(c,0) + 1, it will work.)
Can anyone help?
The reason why you are getting None for t with the append method is because append does not return a value. You can try this instead:
t = y.get("1",[])
t.append(1)
Related
I have created a function which returns a list
def GetAddressContainer(obj,obj1):
mylist = list()
for i in test['adresss']:
addresscotainer = i[id]
return mylist(addresscontainer)
When i call the function -
UkContainer = GetAddressContainer(Postcode,Country)
i get the following error message:
TypeError: 'list' object is not callable in python
Any ideas why i am getting this error and what i would have to update?
The problems seem to be in
return mylist(addresscontainer)
You using parentheses on the list and therefore calling it as a function, that's why you get the error. Without any more code I not entirely sure what to replace it with though.
Issues
The line mylist = list() basically creates an empty list which you can use to store any values. In the code mylist is being called (using (...)) which does not make sense in python since mylist is not a function.
Another issue with the code is that the value of addresscontainer is never being inserted into mylist.
Possible Solutions
So, as per your problem, either of the following solutions can be used:
Append addresscontainer into mylist iteratively within the for loop:
for i in test['adress']:
addresscontainer = i[id]
mylist.append(addresscontainer) # Inserts the value at the end of list
return mylist # Returns the list
[RECOMMENDED] Use list comprehension:
def GetAddressContainer(...):
return [i[id] for i in test['adress']] # Build list using "List Comprehension"
Replace mylist(addresscontainer) with list(addresscontainer) code.
Only list word could be a callable function because it defines a class of any list. And mylist = list() will be an instance of an abstract list, then, not callable.
change mylist = list() to mylist = []
it will create an empty list instead of a list object.
and you are not appending anything to the list.
I have a function below which searches for a dictionary key match using an inputted function parameter. If a key match is found I want the value at index 1 (the team) to change to the desired team inputted when the function is called:
dict1 = {'Messi' : ('Argentina','Barcelona'), 'Ronaldo' : ('Portugal','Juventus'), 'Robben': ('Netherlands','Bayern')}
def setNewTeam(plyr, newTeam):
for x in dict1:
if plyr == x:
dict1[plyr][1] = newTeam
setNewTeam('Messi', 'Manchester')
When I run this code however, I get:
TypeError: 'tuple' object does not support item assignment
I know this must be because tuples are not mutable but there must be a way of making this work since i'm working with dictionaries, can anyone lend a hand here?
Thank you!
As the error message says, you cannot assign new items to tuples because tuples are immutable objects in python.
my_tup = (1,2,3)
my_tup[0] = 2 # TypeError
What you could do is using a list instead:
dict1 = {'Messi' : ['Argentina','Barcelona'], 'Ronaldo' : ['Portugal','Juventus'], 'Robben': ['Netherlands','Bayern']}
def setNewTeam(plyr, newTeam):
for x in dict1:
if plyr == x:
dict1[plyr][1] = newTeam
setNewTeam('Messi', 'Manchester')
Note how lists are created using [] while tuples use ().
dict1 = {'Messi' : ('Argentina','Barcelona'), 'Ronaldo' : ('Portugal','Juventus'), 'Robben': ('Netherlands','Bayern')}
def setNewTeam(plyr, newTeam):
for x in dict1:
if plyr == x:
dict1[plyr] = (dict1[plyr][0], newTeam)
setNewTeam('Messi', 'Manchester')
Since you want to update values, tuple is not the good data-structure. You should use a list.
If you still want to use a tuple, you can build a brand new tuple with :
dict1[plyr] = (dict1[plyr][0], newTeam)
dict1[plyr][1] = newTeam
Tuples are immutable, but lists are not. You can do something like:
list1 = list(dict1[plyr])
list1[1] = newTeam
dict1[plyr] = tuple(list1)
It will add the newTeam to your desired location, and it will still be a tuple.
I've run into the following issue, with my code below. Basically I have a list of objects with an id and a corresponding weight, and I have another list of id's. I want to use only the weights of the objects matching the id's in the second list.
d_weights = [{'d_id':'foo', 'weight': -0.7427}, ...]
d_ids = ['foo', ...]
for dtc_id in d_ids:
d_weight = next((d['weight'] for d in d_weights if d['d_id'] == dtc_id), "")
print str(d_weight)
if str(d_weight) != "":
print "not empty string! "+str(d_weight)
The output for this is:
-0.7427
0.0789
-0.0039
-0.2436
-0.0417
not empty string! -0.0417
Why is only the last one not empty when I can print them fine and they are obviously not equal to an empty string? How do I check that the next() actually returned something before using it?
You haven't correct algorithm.
So d_weight = next((d['weight'] for d in d_weights if d['d_id'] == dtc_id), "") iterate only once.
On every cycle for weight_dict in d_weights: you've got only first dict of d_weights.
Without more data, i can't reproduce your output.
In my case it works fine:
-0.7427
not empty string! -0.7427
-0.327
not empty string! -0.327
Correct code you can find in DhiaTN's answer.
just iterate of the list of the keys and get the values from each dict :
for weight_dict in d_weights
for key in d_ids:
print weight_dict.get(key, "")
I have a list of dictionaries called lod. All dictionaries have the same keys but different values. I am trying to update one specific value in the list of values for the same key in all the dictionaries.
I am attempting to do it with the following for loop:
for i in range(len(lod)):
a=lod[i][key][:]
a[p]=a[p]+lov[i]
lod[i][key]=a
What's happening is each is each dictionary is getting updated len(lod) times so lod[0][key][p] is supposed to have lov[0] added to it but instead it is getting lov[0]+lov[1]+.... added to it.
What am I doing wrong?
Here is how I declared the list of dicts:
lod = [{} for _ in range(len(dataul))]
for j in range(len(dataul)):
for i in datakl:
rrdict[str.split(i,',')[0]]=list(str.split(i,',')[1:len(str.split(i,','))])
lod[j]=rrdict
The problem is in how you created the list of dictionaries. You probably did something like this:
list_of_dicts = [{}] * 20
That's actually the same dict 20 times. Try doing something like this:
list_of_dicts = [{} for _ in range(20)]
Without seeing how you actually created it, this is only an example solution to an example problem.
To know for sure, print this:
[id(x) for x in list_of_dicts]
If you defined it in the * 20 method, the id is the same for each dict. In the list comprehension method, the id is unique.
This it where the trouble starts: lod[j] = rrdict. lod itself is created properly with different dictionaries. Unfortunately, afterwards any references to the original dictionaries in the list get overwritten with a reference to rrdict. So in the end, the list contains only references to one single dictionary. Here is some more pythonic and readable way to solve your problem:
lod = [{} for _ in range(len(dataul))]
for rrdict in lod:
for line in datakl:
splt = line.split(',')
rrdict[splt[0]] = splt[1:]
You created the list of dictionaries correctly, as per other answer.
However, when you are updating individual dictionaries, you completely overwrite the list.
Removing noise from your code snippet:
lod = [{} for _ in range(whatever)]
for j in range(whatever):
# rrdict = lod[j] # Uncomment this as a possible fix.
for i in range(whatever):
rrdict[somekey] = somevalue
lod[j] = rrdict
Assignment on the last line throws away the empty dict that was in lod[j] and inserts a reference to the object represented by rrdict.
Not sure what your code does, but see a commented-out line - it might be the fix you are looking for.
c = d[s[0]] where c is a new variable, d is a dictionary, and s is a list.
What I'm attempting to do is assign the value of a key that is the same as the first element from my list to c. I know the key is in the dictionary, and that the first element of the list is the same as that key. How do I assign the value of that key to a variable? The code I wrote gives me an out of index error.
However, the code:
a = s[0]
c = d[a]
works.
Why doesn't the first attempt work?
This is for Python 2.7 on windows
I have no idea why it is not working for you. Maybe your list is not populated after all. This should work -
>>> d={'world':'hunger'}
>>> s=['world']
>>> d[s[0]]
'hunger'
>>> c = d[s[0]]
>>> c
'hunger'
>>>
Also Python dictionaries have a nifty feature called has_key. It checks if a key is present in that dict or not. I use this to prevent KeyError Exceptions... You could consider using this to prevent untoward crashes.