/usr/lib/python3/dist-packages/pydap/parsers/__init__.py is in python3-pydap 3.2.2+ds1-1ubuntu1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 | """Parsing related functions.
This module defines functions to parse DAP objects, including a base parser for
DDS and DAS responses.
"""
import re
import operator
import ast
from six.moves.urllib.parse import unquote
from six.moves import map
from ..exceptions import ConstraintExpressionError
from ..lib import get_var
def parse_projection(input):
"""Split a projection into items.
The function takes into account server-side functions, and parse slices
into Python slice objects.
Returns a list of names and slices.
"""
def tokenize(input):
start = pos = count = 0
for char in input:
if char == '(':
count += 1
elif char == ')':
count -= 1
elif char == ',' and count == 0:
yield input[start:pos]
start = pos+1
pos += 1
yield input[start:]
def parse(token):
if '(' not in token:
token = token.split('.')
token = [
re.match(r'(.*?)(\[.*\])?$', part).groups()
for part in token]
token = [
(name, parse_hyperslab(slice_ or ''))
for (name, slice_) in token]
return token
return list(map(parse, tokenize(input)))
def parse_selection(expression, dataset):
"""Parse a selection expression into its elements.
This function will parse a selection expression into three tokens: two
variables or values and a comparison operator. Variables are returned as
Pydap objects from a given dataset, while values are parsed using
``ast.literal_eval``.
"""
id1, op, id2 = re.split('(<=|>=|!=|=~|>|<|=)', expression, 1)
op = {
'<=': operator.le,
'>=': operator.ge,
'!=': operator.ne,
'=': operator.eq,
'>': operator.gt,
'<': operator.lt,
}[op]
try:
id1 = get_var(dataset, id1)
except:
id1 = ast.literal_eval(id1)
try:
id2 = get_var(dataset, id2)
except:
id2 = ast.literal_eval(id2)
return id1, op, id2
def parse_ce(query_string):
"""Extract the projection and selection from the QUERY_STRING.
>>> parse_ce('a,b[0:2:9],c&a>1&b<2') # doctest: +NORMALIZE_WHITESPACE
([[('a', ())], [('b', (slice(0, 10, 2),))], [('c', ())]],
['a>1', 'b<2'])
>>> parse_ce('a>1&b<2')
([], ['a>1', 'b<2'])
This function can also handle function calls in the URL, according to the
DAP specification:
>>> ce = 'time&bounds(0,360,-90,90,0,500,00Z01JAN1970,00Z04JAN1970)'
>>> print(parse_ce(ce)) # doctest: +NORMALIZE_WHITESPACE
([[('time', ())]],
['bounds(0,360,-90,90,0,500,00Z01JAN1970,00Z04JAN1970)'])
>>> ce = 'time,bounds(0,360,-90,90,0,500,00Z01JAN1970,00Z04JAN1970)'
>>> print(parse_ce(ce)) # doctest: +NORMALIZE_WHITESPACE
([[('time', ())],
'bounds(0,360,-90,90,0,500,00Z01JAN1970,00Z04JAN1970)'], [])
>>> parse_ce('mean(g,0)')
(['mean(g,0)'], [])
>>> parse_ce('mean(mean(g.a,1),0)')
(['mean(mean(g.a,1),0)'], [])
Returns a tuple with the projection and the selection.
"""
tokens = [token for token in unquote(query_string).split('&') if token]
if not tokens:
projection = []
selection = []
elif re.search('<=|>=|!=|=~|>|<|=', tokens[0]):
projection = []
selection = tokens
else:
projection = parse_projection(tokens[0])
selection = tokens[1:]
return projection, selection
def parse_hyperslab(hyperslab):
"""Parse a hyperslab, returning a Python tuple of slices."""
exprs = [expr for expr in hyperslab[1:-1].split('][') if expr]
out = []
for expr in exprs:
tokens = list(map(int, expr.split(':')))
start = tokens[0]
step = 1
if len(tokens) == 1:
stop = start + 1
elif len(tokens) == 2:
stop = tokens[1] + 1
elif len(tokens) == 3:
step = tokens[1]
stop = tokens[2] + 1
else:
raise ConstraintExpressionError("Invalid hyperslab %s" % hyperslab)
out.append(slice(start, stop, step))
return tuple(out)
class SimpleParser(object):
"""A very simple parser."""
def __init__(self, input, flags=0):
self.buffer = input
self.flags = flags
def peek(self, regexp):
"""Check if a token is present and return it."""
p = re.compile(regexp, self.flags)
m = p.match(self.buffer)
if m:
token = m.group()
else:
token = ''
return token
def consume(self, regexp):
"""Consume a token from the buffer and return it."""
p = re.compile(regexp, self.flags)
m = p.match(self.buffer)
if m:
token = m.group()
self.buffer = self.buffer[len(token):]
else:
raise Exception("Unable to parse token: %s" % self.buffer[:10])
return token
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