D = {'A':
[ ( '1','2' ), ( '3', '4' )],
'B':
[ ( '5','6' ), ( '7','8' ) ]
}
x = '6'
for key in D:
for val in D[key]:
if x in val:
val=('50','60')
print(D)
Hello, I want to make a change at the value of key B, but I wonder why it does not print this:
D = {'A':
[ ( '1','2' ), ( '3','4' ) ],
'B':
[ ( '50','60' ), ( '7','8' ) ]
}
How can I fix it?
By doing val=('50','60') you replace the variable itself, not the content of the list.
for d_val in D.values():
for rank, val in enumerate(d_val):
if x in val:
d_val[rank] = ('50', '80')
val is a local reference to the element. When you overwrite it, you just assign a new tuple to that variable - it has nothing to do with the list that contains it. Instead, you could loop of the list's indexes and update the list directly:
for key in D:
for i in range(len(D[key])):
if x in D[key][i]:
D[key][i] = (50,50)
You can use dictionary comprehension to get this done in one line.
Here's your code to define the dictionary d and value x
d = {'A':
[ ( '1','2' ), ( '3', '4' )],
'B':
[ ( '5','6' ), ( '7','8' ) ]
}
x = '6'
The below one line of code will create the dictionary d again with the new value. To show you that d and r are different only by a small difference, I have retained dictionary d.
r = {k:[(50,60) if x in i else i for i in d[k]] for k in d.keys()}
To ensure there is only one change, I am printing both d and r.
print (d)
print (r)
The output will be as follows:
{'A': [('1', '2'), ('3', '4')], 'B': [('5', '6'), ('7', '8')]}
{'A': [('1', '2'), ('3', '4')], 'B': [(50, 60), ('7', '8')]}