总结一串字符串

Question

I have a file which has bunch of numbers(35463) in it. I want to find the sum of all the numbers, but all the numbers are defined as strings. I know that strings can be turned into an number by float() but as it has 35463 strings, it will be so much work to turn all the strings to numbers, each by each. I wrote this so far:

def main():
    with open ("file", "r") as myfile:
        data = myfile.read().splitlines()

main()

Answer 1

If your file just has a number on each line, eg

0.7506097252963208
0.9176088653062778
0.6762574457637649
0.9782545470065891
...

You can loop through the lines of the file by looping over the open file object. Here I use map to apply float to every line of the file

with open('filename') as f:
    result = sum(map(float, f))

I tried with 350000 entries and it took about 145 milliseconds (on a not very good computer).

Answer 2

Let's say you have create a file of numbers like this:

echo "1234\n2545353\n123245\n3254657687\n8976857463\n" >> numbers.txt

looks like this:

cat numbers.txt                                                                             
1234
2545353
123245
3254657687
8976857463

one possible solution:

# read the lines and trim them
lines = list(map(str.strip, open('numbers.txt').readlines()))
# ['1234', '2545353', '123245', '3254657687', '8976857463', '']

# remove line ending, empty lines
lines = list(filter(lambda item: len(item), nums))
# ['1234', '2545353', '123245', '3254657687', '8976857463']

# convert to numbers
nums = list(map(float, lines))
# [1234.0, 2545353.0, 123245.0, 3254657687.0, 8976857463.0]

# and now we simply sum 'em
total = sum(nums)
# 12234184982.0