CODEWITHSUNDEEP
pythonpython-2.7list
nice_remark
nice_remark

Reputation: 337

Iterate through a list, divide values, store in new list

In the code I have series of lists, each one containing the same number of entries. What I want to do now is iterate through the list and divide one list index by the other. 

threads = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
dsk_indpt_PI = [99, 197, 295, 387, 391, 406, 407, 416, 424, 426, 425, 439]

avg_val = []
for x in threads:
    result = dsk_indpt_PI[x]/threads[x]
    avg_val.append(result[x])

I am unsure if the above method works, previous methods I ran into the issue where it could not do division between type int and type list. Would the above example work better? If not, what should be changed to have it function as desired? Thank you.

Upvotes: 0

Views: 1641

Answers (5)

Adam Smith
Adam Smith

Reputation: 54213

The better way to do this is to use zip.

You can try this:

avg_vals = []
for thread, dsk_ind in zip(threads, dsk_indpt_PI):
    avg_vals.append(dsk_ind / thread)

zip takes two (or more) iterables and combines them into one list of tuples with length equal to the shortest iterable.

Upvotes: 2

Aaditya Ura
Aaditya Ura

Reputation: 12669

Use pythonic way , One line solution:

print([item[1]/item[0] for item in zip(threads,dsk_indpt_PI)])

output:

[99.0, 98.5, 98.33333333333333, 96.75, 78.2, 67.66666666666667, 58.142857142857146, 52.0, 47.111111111111114, 42.6, 38.63636363636363, 36.583333333333336]

above list comprehension is same as:

divide=[]
for item in zip(threads,dsk_indpt_PI):
    divide.append(item[1]/item[0])

print(divide)

Upvotes: 0

George_E -old
George_E -old

Reputation: 188

threads = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
dsk_indpt_PI = [99, 197, 295, 387, 391, 406, 407, 416, 424, 426, 425, 439]

avg_val = []
for x in range(len(threads)):
    result = dsk_indpt_PI[x]/threads[x]
    avg_val.append(result)

print(avg_val)

Object is not iterable, and you cannot use result[x] as it is not a list and is being reset every time anyway.

Upvotes: 0

Mek-OY
Mek-OY

Reputation: 54

If you are iterating over a list with a regular for loop, you will get the values, and not the indices. If you want the indices, you could use for i in range(len(myList)): which would give every index i in your list. Alternatively, you could use for index, value in enumerate(myList) if you want both the index and the value.

Upvotes: 0

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 476739

If you iterate over a list you obtain the values of the list, not the indices.

You can use range(len(..)) to obtain the indices. Furthermore the result is result, not result[x] to store it into the avg_val:

avg_val = []
for x in range(len(threads)):
    result = dsk_indpt_PI[x]/threads[x]
    avg_val.append(result)

But a more Pythonic version will use zip:

avg_val = []
for a,b in zip(dsk_indpt_PI, threads):
    result = a/b
    avg_val.append(resul)

and we can turn this in list comprehension:

avg_val = [a/b for a,b in zip(dsk_indpt_PI, threads)]

List comprehension is a way to create a list in a more elegant way by writing generator syntax between square brackets.

Upvotes: 2

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