Databases
StackOverflow2013
Postsdbo
POUsing pyparsing to parse a list from a string with special characters
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POUsing pyparsing to parse a list from a string with special characters
    primarykey
    data
    text
    <p>I'd like to parse a list from a string field that may contain special characters such as \ \n \r \n \t and expand over multiple lines. Currently, I have to parse the string first, clean it up, then apply the list grammar on the that clean string. It works ok but just wondering if there's a better way.</p> <p>This is what I current have</p> <pre><code>str_ = QuotedString('"',escChar='\\',multiline=True) #grammar for str str_.setParseAction(lambda pr: pr[0].replace('\\n',' ')\ .replace('\\r', ' ')\ .replace('\r', ' ')\ .replace('\t', ' ')) list_G = delimitedList(Word(printables))('mlist') #grammar for list def pa(st,locn,pr): return list_G.parseString(pr.mystr) mylist = Group(str_('mystr').addParseAction(pa)) #read in the str then re-parse G = Keyword("LIST") + mylist('thelist') + ';' #grammar for the whole thing s = 'LIST "one,two,three" ;' </code></pre> <p>Edit: Instead of Word(printables) in list_G, changed to </p> <pre><code>var_grammar = Word(alphas+"_", alphanums + "_") #"_a,a2b_,.." num_grammar = Regex(r"[+-]?\d+(:?\.\d*)?(:?[eE][+-]?\d+)?")('num') list_G = delimitedList(var_grammar|num_grammar)('mlist') #grammar for list G = Keyword("LIST") + '"' + mylist('thelist') + '"' + ';' </code></pre> <p>The reason that forces me to do the clean up above that replaces <code>"\\n", "\\r" with ' '</code> is because I read in string from a file that literally contains the the charactors <code>\n, \r</code> and those are not parsable by var_name or num (they are not printable)</p> <p>This is an example of a (raw) string in the file :</p> <pre><code>LIST "one,two, three, \nfour,\rfive"; </code></pre> <p>Do you have any suggestion about this ?</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USVu Nguyen
    1. USVu Nguyen
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POUsing pyparsing to parse a list from a string with special characters
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POUsing pyparsing to parse a list from a string with special characters
      1. This table or related slice is empty.
      1. VTUpMod
    1. COCan you edit your question to include some special characters in `s`, and show what the problem is if you don't parse in this two-step manner?
      singulars
      1. POUsing pyparsing to parse a list from a string with special characters
      1. USPaulMcG
    2. COIf you actually have the characters of a backslash and an 'n' in the string itself, then define an expression like `unwanted = Word('\\','rnt',exact=2)`, and then do `G.ignore(unwanted)`.
      singulars
      1. POUsing pyparsing to parse a list from a string with special characters
      1. USPaulMcG
    3. COthat seems to be a nice solution -- should be equivalent with current my hack around that replaces those `\t \n \r` with space right after reading in the file and before parsing it. Thanks
      singulars
      1. POUsing pyparsing to parse a list from a string with special characters
      1. USVu Nguyen
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload