I'm making a function to modify the elements in a list, but it doesn't change all the way through... My function is:
def modifyValues(l):
for x in l:
if x == 1:
l[x] = 'a'
elif x == 2:
l[x] = 'b'
elif x == 3:
l[x] = 'c'
print (l)
when
modifyValues([1, 2, 3, 2, 3, 1, 2, 2])
the output is:
['a', 'b', 'c', 2, 3, 1, 2, 2]
Why doesn't it change every value?
When you iterate through the loop, you are iterating the loop elements and not the indexes.
You need to use enumerate to get the indexes along with the values.
A small demo can be
def modifyValues(l):
for i,x in enumerate(l): # Use enumerate here.
if x == 1:
l[i] = 'a'
elif x == 2:
l[i] = 'b'
elif x == 3:
l[i] = 'c'
print (l)
Output
['a', 'b', 'c', 'b', 'c', 'a', 'b', 'b']
instead of using ""for x in (l) use for x in range (len(l))"" as x in (l) uses the values, not indices(indexing). Here's how you can do it:
def modifyValues(l):
for x in range(len(l)):
if l[x] == 1:
l[x] = 'a'
elif l[x] == 2:
l[x] = 'b'
elif l[x] == 3:
l[x] = 'c'
print(l)
modifyValues([1, 2, 3, 2, 3, 1, 2, 2])
You should dictionary instead to change item in the list.
>>> def modifyValues(l):
... d = {'a': 1, 'b': 2, 'c': 3}
... modifyl = [k for i in l for k in d if d[k] == i]
... print(modifyl)
...
>>> modifyValues([1, 2, 3, 2, 3, 1, 2, 2])
['a', 'b', 'c', 'b', 'c', 'a', 'b', 'b']
>>>
You can also use the ascii_lowercase constant from string
>>> from string import ascii_lowercase
>>> def modifyValues(l):
... modifyl = [v for i in l for k, v in enumerate(ascii_lowercase, 1) if i == k]
... print(modifyl)
...
>>> modifyValues([1, 2, 3, 2, 3, 1, 2, 2])
['a', 'b', 'c', 'b', 'c', 'a', 'b', 'b']
Your code is incorrect, because when you iterate your list def modifyValues(l):
for x in l: // the value of x will be the position of value
if x == 1:// your if condition does not check for the value in the list, it only checks the position.
l[x] = 'a'
elif x == 2:
l[x] = 'b'
elif x == 3:
l[x] = 'c'
print (l)
To improve your code use this as your if condition
if l[x] == 1
