使用正则表达式提取数据：Python

Question

这个问题的基本大纲是读取文件，使用re.findall()查找整数，查找[0-9]+的正则表达式，然后将提取的字符串转换为整数并对整数求和。

我在附加列表时遇到了麻烦。从我下面的代码中，它只是附加了该行的第一个（0）索引。请帮我。谢谢。

import re
hand = open ('a.txt')
lst = list()
for line in hand:
    line = line.rstrip()
    stuff = re.findall('[0-9]+', line) 
    if len(stuff)!= 1  : continue
    num = int (stuff[0])
    lst.append(num)
print sum(lst)

Answer 1

太好了，感谢您包含整个 txt 文件！您的主要问题出在if len(stuff)... 行中，如果stuff 里面有零个东西，当它有2,3 等等时，它就会跳过。您只保留长度为 1 的 stuff 列表。我将 cmets 放入代码中，但如果有不清楚的地方，请提出任何问题。

import re
hand = open ('a.txt')
str_num_lst = list()
for line in hand:
    line = line.rstrip()
    stuff = re.findall('[0-9]+', line)
    #If we didn't find anything on this line then continue
    if len(stuff) == 0: continue
    #if len(stuff)!= 1: continue #<-- This line was wrong as it skip lists with more than 1 element

    #If we did find something, stuff will be a list of string:
    #(i.e. stuff = ['9607', '4292', '4498'] or stuff = ['4563'])
    #For now lets just add this list onto our str_num_list
    #without worrying about converting to int.
    #We use '+=' instead of 'append' since both stuff and str_num_lst are lists
    str_num_lst += stuff

#Print out the str_num_list to check if everything's ok
print str_num_lst

#Get an overall sum by looping over the string numbers in the str_num_lst
#Can convert to int inside the loop
overall_sum = 0
for str_num in str_num_lst:
    overall_sum += int(str_num)

#Print sum
print 'Overall sum is:'
print overall_sum

编辑：

你是对的，将整个文件作为一行读取是一个很好的解决方案，而且不难做到。查看this post。下面是代码的样子。

import re

hand = open('a.txt')
all_lines = hand.read() #Reads in all lines as one long string
all_str_nums_as_one_line = re.findall('[0-9]+',all_lines)
hand.close() #<-- can close the file now since we've read it in

#Go through all the matches to get a total
tot = 0
for str_num in all_str_nums_as_one_line:
    tot += int(str_num)

print('Overall sum is:',tot) #editing to add ()

Answer 2

import re
ls=[];
text=open('C:/Users/pvkpu/Desktop/py4e/file1.txt');
for line in text:
    line=line.rstrip();
    l=re.findall('[0-9]+',line);
    if len(l)==0:
        continue
    ls+=l
for i in range(len(ls)):
    ls[i]=int(ls[i]);
print(sum(ls));