[Tutor] Escape characters in strings

[Grimmtooth]

> | Example:
> |
> | 12/13 14:04:53 2> S:<STX>L.TG23  Y1           12007030050020C100021340
> | 12/13 14:04:53 2> S:12888888881003030000000001249000212011213140434210
> | 12/13 14:04:53 2> S:10125414C200344012888888881=0512101543211234567800
> | 12/13 14:04:53 2> S:1     700000000740   0242C00000000000000EN00420107
> | 12/13 14:04:53 2> S:6O02450U300001000\300009990\000000000999\950U30000
> | 12/13 14:04:53 2> S:1000\300002500\000000000250<ETX>.
>
> Is this from a log file?  How are you reading the data?  Can you show
> us the code?

1) Yes and no.

2) (a) either the user pastes this data into a wxWindows Text Control then I
GetValue() it or else it is read from a logfile directly using readlines()
into an array.  In the current case, I've hardcoded the text in using a """
triple-quoted string.  The problem occurs no matter which way it goes.

3) I could, but it would be a lot of code. Let me paraphrase it:

   first, get code from text control or log file.

   then, using a function Stitch(), I locate all lines beginning with S:
after the 2> by first slicing [] them out then concatenating them together
with '+'. This returns one continuous string.

	for i in s:
		x = i[18:-1]    # first 18 are time stamp, last is CR. Trim both.

		if len(x) > 0:
			if x[0] == 'S':
				snd.append(x)

   then, I pass the string to a Parser class.  This in turn slices out
particular parts of the long string and assigns them to additional classes,
each designed to parse the particular data it is passed.

class BaseElement:
	def	__init__(self, parent):
		pass

	def Show(self):
		pass

class AdditionalAmounts(BaseElement):

	data	=	None

	def __init__(self, parent, txt):
		self.data, parent.remainder	=	lllvar(txt)


def llvar(data):
	len	=	int(data[:2])
	return(data[2:len+2], data[len+2:])


the BaseElement class is an empty, defined to give me a None if I don't
override the __init__ and Show methods. Assuming that I've sliced off
everything prior to the part of interest already (which I have), the above
code fragments are the ones that get processed. First, the string is passed
to AdditionalAmounts.__init__().  __init__() calls llvar() to seperate the
data and from the remainder of the log entry (an llvar is a data field that
is preceded by two digits indicating how many bytes the data contains). The
process of actually processing the data is where I end up tripping over the
escaped \ characters.


> If you do want to eval() the string you can replace( "\\" , "\\\\" )
> to escape all backslashes first.

Doesn't work, that was the first thing I tried. For some reason Python's not
finding the '\' because it thinks '\300' is a single character rather than
four.

Even 'print x' will hide the \ in this case.



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