[Tutor] how to get blank value

[amrita at iisermohali.ac.in]

Thanks for help Sir but with these commands it is showing error:-

ph08001 at sys53:~> python trip.py
Traceback (most recent call last):
  File "trip.py", line 6, in <module>
    from pyparsing import *
ImportError: No module named pyparsing


> Ok, I've seen various passes at this problem using regex, split('='),
> etc.,
> but the solutions seem fairly fragile, and the OP doesn't seem happy with
> any of them.  Here is how this problem looks if you were going to try
> breaking it up with pyparsing:
> - Each line starts with an integer, and the string "ALA"
> - "ALA" is followed by a series of "X = 1.2"-type attributes, where the
> value part might be missing.
>
> And to implement (with a few bells and whistles thrown in for free):
>
> data = """48 ALA H = 8.33 N = 120.77 CA = 55.18 HA = 4.12 C = 181.50
> 104 ALA H = 7.70 N = 121.21 CA = 54.32 HA = 4.21 C =
> 85 ALA H = 8.60 N =  CA =  HA = 4.65 C =""".splitlines()
>
>
> from pyparsing import *
>
> # define some basic data expressions
> integer = Word(nums)
> real = Combine(Word(nums) + "." + Word(nums))
>
> # use parse actions to automatically convert numeric
> # strings to actual numbers at parse time
> integer.setParseAction(lambda tokens:int(tokens[0]))
> real.setParseAction(lambda tokens:float(tokens[0]))
>
> # define expressions for 'X = 1.2' assignments; note that the
> # value might be missing, so use Optional - we'll fill in
> # a default value of 0.0 if no value is given
> keyValue = Word(alphas.upper()) + '=' + \
>             Optional(real|integer, default=0.0)
>
> # define overall expression for the data on a line
> dataline = integer + "ALA" + OneOrMore(Group(keyValue))("kvdata")
>
> # attach parse action to define named values in the returned tokens
> def assignDataByKey(tokens):
>     for k,_,v in tokens.kvdata:
>         tokens[k] = v
> dataline.setParseAction(assignDataByKey)
>
> # for each line in the input data, parse it and print some of the data
> fields
> for d in data:
>     print d
>     parsedData = dataline.parseString(d)
>     print parsedData.dump()
>     print parsedData.CA
>     print parsedData.N
>     print
>
>
> Prints out:
>
> 48 ALA H = 8.33 N = 120.77 CA = 55.18 HA = 4.12 C = 181.50
> [48, 'ALA', ['H', '=', 8.3300000000000001], ['N', '=', 120.77], ['CA',
> '=',
> 55.18], ['HA', '=', 4.1200000000000001], ['C', '=', 181.5]]
> - C: 181.5
> - CA: 55.18
> - H: 8.33
> - HA: 4.12
> - N: 120.77
> - kvdata: [['H', '=', 8.3300000000000001], ['N', '=', 120.77], ['CA', '=',
> 55.18], ['HA', '=', 4.1200000000000001], ['C', '=', 181.5]]
> 55.18
> 120.77
>
> 104 ALA H = 7.70 N = 121.21 CA = 54.32 HA = 4.21 C =
> [104, 'ALA', ['H', '=', 7.7000000000000002], ['N', '=',
> 121.20999999999999],
> ['CA', '=', 54.32], ['HA', '=', 4.21], ['C', '=', 0.0]]
> - C: 0.0
> - CA: 54.32
> - H: 7.7
> - HA: 4.21
> - N: 121.21
> - kvdata: [['H', '=', 7.7000000000000002], ['N', '=', 121.20999999999999],
> ['CA', '=', 54.32], ['HA', '=', 4.21], ['C', '=', 0.0]]
> 54.32
> 121.21
>
> 85 ALA H = 8.60 N =  CA =  HA = 4.65 C =
> [85, 'ALA', ['H', '=', 8.5999999999999996], ['N', '=', 0.0], ['CA', '=',
> 0.0], ['HA', '=', 4.6500000000000004], ['C', '=', 0.0]]
> - C: 0.0
> - CA: 0.0
> - H: 8.6
> - HA: 4.65
> - N: 0.0
> - kvdata: [['H', '=', 8.5999999999999996], ['N', '=', 0.0], ['CA', '=',
> 0.0], ['HA', '=', 4.6500000000000004], ['C', '=', 0.0]]
> 0.0
> 0.0
>
>
> Learn more about pyparsing at http://pyparsing.wikispaces.com.
>
> -- Paul
>
>
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
>


Amrita Kumari
Research Fellow
IISER Mohali
Chandigarh
INDIA