Question

我正在尝试为存储在文件中的类似于下面的字符串创建正则表达式模式。目的是为任何行获取任何列，行不必在一行上。例如，请考虑以下文件：

"column1a","column2a","column
  3a,",             #entity 1
"column\"this is, a test\"4a"
"column1b","colu
     mn2b,","column3b",             #entity 2
"column\"this is, a test\"4b"
"column1c,","column2c","column3c",             #entity 3
"column\"this is, a test\"4c"

每个实体由四列组成，实体2的第4列为＆＃34;列\＆＃34;这是，实验3的第2列测试＆＃34; 4b＆＃34;＆＃34; column2c＆＃34 ;.每列以引号开头并以引号结束，但是您必须小心，因为某些列已转义引号。提前谢谢！

Answer 1

你可以这样做，即

阅读整个文件。
根据换行符前面的换行符分割输入。
迭代spitted元素并再次对逗号（以及下面的可选换行符）进行拆分，前面和后面跟着双引号。

代码：

import re
with open(file) as f:
    fil = f.read()
    m = re.split(r'(?<!,)\n', fil.strip())
    for i in m:
        print(re.split('(?<="),\n?(?=")', i))

输出：

['"column1a"', '"column2a"', '"column3a,"', '"column\\"this is, a test\\"4a"']
['"column1b"', '"column2b,"', '"column3b"', '"column\\"this is, a test\\"4b"']
['"column1c,"', '"column2c"', '"column3c"', '"column\\"this is, a test\\"4c"']

这是支票..

$ cat f
"column1a","column2a","column3a,",
"column\"this is, a test\"4a"
"column1b","column2b,","column3b",
"column\"this is, a test\"4b"
"column1c,","column2c","column3c",
"column\"this is, a test\"4c"
$ python3 f.py
['"column1a"', '"column2a"', '"column3a,"', '"column\\"this is, a test\\"4a"']
['"column1b"', '"column2b,"', '"column3b"', '"column\\"this is, a test\\"4b"']
['"column1c,"', '"column2c"', '"column3c"', '"column\\"this is, a test\\"4c"']

f是输入文件名，f.py是包含python脚本的文件名。

Answer 2

你的问题非常熟悉我每个月必须处理三次:)除了我没有使用python来解决它，但我可以'翻译'我通常做的事情：

text = r'''"column1a","column2a","column
  3a,",
"column\"this is, a test\"4a"
"column1a2","column2a2","column3a2","column4a2"
"column1b","colu
     mn2b,","column3b",             
"column\"this is, a test\"4b"
"column1c,","column2c","column3c",
"column\"this is, a test\"4c"'''

import re

# Number of columns one line is supposed to have
columns = 4
# Temporary variable to hold partial lines
buffer = ""
# Our regex to check for each column
check = re.compile(r'"(?:[^"\\]*|\\.)*"')

# Read the file line by line
for line in text.split("\n"):
    # If there's no stored partial line, this is a new line
    if buffer == "":
        # Check if we get 4 columns and print, if not, put the line
        # into buffer so we store a partial line for later
        if len(check.findall(line)) == columns:
            print matches
        else:
            # use line.strip() if you need to trim whitespaces
            buffer = line
    else:
        # Update the variable (containing a partial line) with the
        # next line and recheck if we get 4 columns
        # use line.strip() if you need to trim whitespaces
        buffer = buffer + line
        # If we indeed get 4, our line is complete and print
        # We must not forget to empty buffer now that we got a whole line
        if len(check.findall(buffer)) == columns:
            print matches
            buffer = ""
        # Optional; always good to have a safety backdoor though
        # If there is a problem with the csv itself like a weird unescaped
        # quote, you send it somewhere else
        elif len(check.findall(buffer)) > columns:
            print "Error: cannot parse line:\n" + buffer
            buffer = ""

ideone demo

python中的正则表达式使用引号

2 个答案: