从文件读取时去除空格和新行

Question

我有以下代码，它在从文件读取时成功去除了行尾字符，但对于任何前导和尾随空格都没有这样做（我希望保留它们之间的空格！）

实现这一目标的最佳方法是什么？ （注意，这是一个具体的例子，所以不是一般的字符串剥离方法的重复）

我的代码：（尝试使用测试数据：“Mr Moose”（未找到）如果您尝试 “Mr Moose”（即 Moose 后面的空格）会起作用。

#A COMMON ERROR is leaving in blank spaces and then finding you cannot work with the data in the way you want!

"""Try the following program with the input: Mr Moose
...it doesn't work..........
but if you try "Mr Moose " (that is a space after Moose..."), it will work!
So how to remove both new lines AND leading and trailing spaces when reading from a file into a list. Note, the middle spaces between words must remain?
"""

alldata=[]
col_num=0
teacher_names=[]
delimiter=":"

with open("teacherbook.txt") as f:
      for line in f.readlines():
            alldata.append((line.strip()))
      print(alldata)


      print()
      print()

      for x in alldata: 
             teacher_names.append(x.split(delimiter)[col_num]) 

      teacher=input("Enter teacher you are looking for:")
      if teacher in teacher_names: 
            print("found")
      else:
            print("No")

期望的输出，关于生成列表 alldata

['Mr Moose:Maths', 'Mr Goose:History', 'Mrs Congenelipilling:English']

即 - 删除开头、分隔符之前或之后的所有前导和尾随空格。必须留下诸如 Mr Moose 等单词之间的空格。

教科书内容：

Mr Moose : Maths
Mr Goose: History
Mrs Congenelipilling: English

提前致谢

Answer 1

你可以使用正则表达式：

txt='''\
Mr Moose : Maths
Mr Goose: History
Mrs Congenelipilling: English'''

>>> [re.sub(r'\s*:\s*', ':', line).strip() for line in txt.splitlines()]
['Mr Moose:Maths', 'Mr Goose:History', 'Mrs Congenelipilling:English']

所以你的代码变成了：

import re
col_num=0
teacher_names=[]
delimiter=":"

with open("teacherbook.txt") as f:
    alldata=[re.sub(r'\s*{}\s*'.format(delimiter), delimiter, line).rstrip() for line in f]
    print(alldata)

    for x in alldata: 
         teacher_names.append(x.split(delimiter)[col_num]) 
    print(teacher_names)  

打印：

['Mr Moose:Maths', 'Mr Goose:History', 'Mrs Congenelipilling:English']
['Mr Moose', 'Mr Goose', 'Mrs Congenelipilling']

关键部分是正则表达式：

re.sub(r'\s*{}\s*'.format(delimiter), delimiter, line).rstrip()

          ^                          0 to unlimited spaced before the delimiter
            ^                        place for the delimiter
              ^                      unlimited trailing space

Interactive Demo

---

对于全 Python 解决方案，我将使用 str.partition 获取分隔符的左侧和右侧，然后根据需要去除空格：

alldata=[]    
with open("teacherbook.txt") as f:
    for line in f:
        lh,sep,rh=line.rstrip().partition(delimiter)
        alldata.append(lh.rstrip() + sep + rh.lstrip())

同样的输出

---

另一个建议。您的数据更适合dict，而不是列表。

你可以这样做：

di={}
with open("teacherbook.txt") as f:
    for line in f:
        lh,sep,rh=line.rstrip().partition(delimiter)
        di[lh.rstrip()]=rh.lstrip()

或理解版：

with open("teacherbook.txt") as f:
    di={lh.rstrip():rh.lstrip() 
          for lh,_,rh in (line.rstrip().partition(delimiter) for line in f)}

然后像这样访问：

>>> di['Mr Moose']
'Maths'

Answer 2

无需使用readlines()，您可以简单地遍历文件对象以获取每一行，并使用strip() 删除\n 和空格。因此，您可以使用此列表推导；

with open('teacherbook.txt') as f:
    alldata = [':'.join([value.strip() for value in line.split(':')]) 
               for line in f]
    print(alldata)

---

输出；

['Mr Moose:Maths', 'Mr Goose:History', 'Mrs Congenelipilling:English']

Answer 3

变化：

teacher_names.append(x.split(delimiter)[col_num])

到：

teacher_names.append(x.split(delimiter)[col_num].strip())

Answer 4

删除开头、分隔符之前或之后的所有前导和尾随空格。必须留下诸如 Mr Moose 等单词之间的空格。

您可以在分隔符处拆分字符串，从它们中去除空格，然后将它们重新连接在一起：

for line in f.readlines():
    new_line = ':'.join([s.strip() for s in line.split(':')])
    alldata.append(new_line)

示例：

>>> lines = ['  Mr Moose :   Maths', ' Mr Goose :  History  ']
>>> lines
['  Mr Moose :   Maths', ' Mr Goose :  History  ']
>>> data = []
>>> for line in lines:
    new_line = ':'.join([s.strip() for s in line.split(':')])
    data.append(new_line)


>>> data
['Mr Moose:Maths', 'Mr Goose:History']

Answer 5

您可以使用正则表达式轻松完成 - re.sub：

import re

re.sub(r"[\n \t]+$", "", "aaa \t asd \n ")
Out[17]: 'aaa \t asd'

第一个参数模式 - [所有要删除的字符]++ - 一个或多个匹配项$$ - 字符串结尾

https://docs.python.org/2/library/re.html

Answer 6

使用 string.rstrip('something') 你可以像这样从字符串的右端删除那个'something'：

a = 'Mr Moose \n'

print a.rstrip(' \n') # prints 'Mr Moose\n' instead of 'Mr Moose \n\n'