将字符串列表转换为浮点列表并获取所有值的总和

Question

I have the following list in python 3.

['12 32.12 453\n', '54 123 65\n', '12 32\n', '12 32 54 765 876\n']

How do I remove the \\n from the end of each entry? And how do I convert the list to

[12.0, 32.12, 453.0, 54.0, 123.0, 65.0, 12.0, 32.0, 12.0, 32.0, 54.0, 765.0, 876.0]

?

I need a way to convert each number to a float and add them all together to get a sum. this This is my code so far:

def calc_sum(filename):
    new_list = []
    try:
        file = open(filename)
    except:
        print("oops")
        return None
    line = file.readlines()
    print(line)

Answer 1

Convert to a list of floats:

>>> a = ['12 32.12 453\n', '54 123 65\n', '12 32\n', '12 32 54 765 876\n']    
>>> k = [float(y) for lst in (x.split() for x in a) for y in lst]
>>> k
[12.0, 32.12, 453.0, 54.0, 123.0, 65.0, 12.0, 32.0, 12.0, 32.0, 54.0, 765.0, 876.0]

Get the sum:

>>> sum(k)
2522.12

All in one line:

>>> sum(float(y) for lst in (x.split() for x in a) for y in lst)
2522.12

Explanation :

To see what's going on, here's equivalent code without the use of list/generator comprehensions:

k = []
for x in a:
    x = x.split()
    k.append(x)

k is now [['12', '32.12', '453'], ['54', '123', '65'], ['12', '32'], ['12', '32', '54', '765', '876']] . We've got rid of the newline characters and have a list of lists, each inner list containing strings (which can be converted to floating point numbers). Next, we flatten the list:

m = []
for sublist in k:
    for x in sublist:
        m.append(x)     

m is ['12', '32.12', '453', '54', '123', '65', '12', '32', '12', '32', '54', '765', '876'] . Finally, we convert all string values to floats:

k = []
for x in m:
    k.append(float(x))

k is [12.0, 32.12, 453.0, 54.0, 123.0, 65.0, 12.0, 32.0, 12.0, 32.0, 54.0, 765.0, 876.0] and sum(k) will yield the sum over all the elements.

Answer 2

Try using a map :

>>> x = ['12 32.12 453\n', '54 123 65\n', '12 32\n', '12 32 54 765 876\n']
>>> map(float, ''.join(x).split())
[12.0, 32.12, 453.0, 54.0, 123.0, 65.0, 12.0, 32.0, 12.0, 32.0, 54.0, 765.0, 876.0]
>>> 

Answer 3

The strip method will remove trailing characters and the split method will split each line at spaces. Then use float to convert each chunk from string to float and sum to get a sum. Iterate over lines, sum line partials and you are done.

def calc_sum(filename)
    result = 0.0

    with open(filename) as stream:
        for line in stream:
            values = line.strip("\n").split(" ")
            result += sum(float(x) for x in values)

    return result