python - 反转列表中行的顺序

Question

我在用 Python 编写程序时遇到一些困难。我希望程序读取一组字符之间的行，反转行的顺序，然后将它们写入新文件中。输入为:

AN10 G17 G21 G90
N20 '2014_12_08_Banding_Test_4
N30 M3 S1B
N40G00X0.000Y0.000Z17.000
N50 G00X0.001Y0.001Z17.000
N60 G01Z0.000F3900.0
N70 G01X0.251
N80 G01X149.999
N90 G01Y0.251
N100 G01X149.749
N110 G01X149.499Z-8.169
N120 G01X148.249Z-8.173
N130 G01X146.999Z-8.183
N140 G01X145.499Z-8.201
...
N3140 G01Y0.501

到目前为止我的代码是:

with open('Source.nc') as infile, open('Output.nc', 'w') as outfile:
    copy = False
    strings_A = ("G01Y", ".251")
    strings_B = ("G01Y", ".501")
    content = infile.readlines()
    for lines in content:
        lines.splitlines(1)
        if all(x in lines for x in strings_A):
            copy = True
        elif all(x in lines for x in strings_B):
            copy = False
        elif copy:
            outfile.writelines(reversed(lines))

我认为我无法理解行和多行字符串之间的区别。我真的很感激这里的一些帮助!

预先感谢，亚瑟

Answer 1

如果字符串包含换行符\n，则该字符串有多行。

您可以将文件视为包含换行符的长字符串:

s = infile.read()

或者您可以将其视为行列表:

lines = infile.readlines()

如果您有一个多行字符串，您可以将其拆分为行列表:

lines = s.splitlines(False)
# which is basically a special form of:
lines = s.split('\n')

如果您想逐行处理文件，以下所有方法都是等效的(如果效率不高，则有效):

with open(filename, 'r') as f:
  s = f.read()
  lines = s.splitlines()
  for line in lines:
    # do something
    pass

with open(filename, 'r') as f:
  lines = f.readlines()
  for line in lines:
    # do something
    pass

# this last option is the most pythonic one, 
#   it uses the fact that any file object can be treated as a list of lines
with open(filename, 'r') as f
  for line in f:
    # do something
    pass

编辑现在是您问题的解决方案:

with open('Source.nc') as infile, open('Output.nc', 'w') as outfile:
    copy = False
    strings_A = ("G01Y", ".251")
    strings_B = ("G01Y", ".501")
    target_lines = []
    for line in infile:
        if copy and all(x in line for x in strings_B):
            outfile.writelines(reversed(target_lines))
            break

        if copy:
          target_lines.append(line)

        if all(x in line for x in strings_A):
            copy = True

这将复制与 all(x in line for x in strings_A) 匹配的行和与 all(x in line for x in strings_B) 匹配的行之间的所有行 code> 以相反的顺序进入输出文件。识别行不包含在输出中(我希望这是意图)。if 子句的顺序是为了实现这一目标而特意设计的。

还要注意，您使用的识别测试 (all(x in line for x in strings_A)) 是作为子字符串搜索而不是单词匹配，同样，我不知道是否可以是你的意图。

编辑2回复评论:

with open('Source.nc') as infile, open('Output.nc', 'w') as outfile:
    strings_A = ("G01Y", ".251")
    strings_B = ("G01Y", ".501")
    do_reverse = False
    lines_to_reverse = []
    for line in infile:
        if all(x in line for x in strings_B):
           do_reverse = False
           outfile.writelines(reversed(lines_to_reverse))
           outfile.writeline(line)
           continue

        if do_reverse:
          lines_to_reverse.append(line)
          continue
        else:
          outfile.writeline(line)

        if all(x in line for x in strings_A):
          do_reverse = True
          lines_to_reverse = []