Cleaned up code
This commit is contained in:
Terry Cain
parent
a5895db4f8
commit
77fcafca18
3 changed files with 258 additions and 74 deletions
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@ -69,7 +69,8 @@ def get_filter_expression(expr, names, values):
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# Remove all spaces, tbf we could just skip them in the next step.
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# The number of known options is really small so we can do a fair bit of cheating
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expr = list(re.sub('\s', '', expr)) # 'Id>5ANDattribute_exists(test)ORNOTlength<6'
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#expr = list(re.sub('\s', '', expr)) # 'Id>5ANDattribute_exists(test)ORNOTlength<6'
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expr = list(expr)
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# DodgyTokenisation stage 1
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def is_value(val):
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@ -90,7 +91,11 @@ def get_filter_expression(expr, names, values):
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while len(expr) > 0:
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current_char = expr.pop(0)
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if current_char == ',': # Split params ,
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if current_char == ' ':
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if len(stack) > 0:
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tokens.append(stack)
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stack = ''
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elif current_char == ',': # Split params ,
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if len(stack) > 0:
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tokens.append(stack)
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stack = ''
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@ -113,6 +118,9 @@ def get_filter_expression(expr, names, values):
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if len(stack) > 0:
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tokens.append(stack)
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def is_op(val):
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return val in ('<', '>', '=', '>=', '<=', '<>', 'BETWEEN', 'IN', 'AND', 'OR', 'NOT')
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# DodgyTokenisation stage 2, it groups together some elements to make RPN'ing it later easier.
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tokens2 = []
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token_iterator = iter(tokens)
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@ -122,17 +130,30 @@ def get_filter_expression(expr, names, values):
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next_token = six.next(token_iterator)
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while next_token != ')':
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try:
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next_token = int(next_token)
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except ValueError:
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try:
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next_token = float(next_token)
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except ValueError:
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pass
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tuple_list.append(next_token)
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next_token = six.next(token_iterator)
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tokens2.append(tuple(tuple_list))
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# Sigh, we only want to group a tuple if it doesnt contain operators
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if any([is_op(item) for item in tuple_list]):
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tokens2.append('(')
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tokens2.extend(tuple_list)
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tokens2.append(')')
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else:
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tokens2.append(tuple(tuple_list))
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elif token == 'BETWEEN':
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op1 = six.next(token_iterator)
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field = tokens2.pop()
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op1 = int(six.next(token_iterator))
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and_op = six.next(token_iterator)
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assert and_op == 'AND'
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op2 = six.next(token_iterator)
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tokens2.append('BETWEEN')
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tokens2.append((op1, op2))
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op2 = int(six.next(token_iterator))
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tokens2.append(['between', field, op1, op2])
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elif is_function(token):
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function_list = [token]
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@ -161,39 +182,38 @@ def get_filter_expression(expr, names, values):
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def is_number(val):
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return val not in ('<', '>', '=', '>=', '<=', '<>', 'BETWEEN', 'IN', 'AND', 'OR', 'NOT')
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def is_op(val):
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return val in ('<', '>', '=', '>=', '<=', '<>', 'BETWEEN', 'IN', 'AND', 'OR', 'NOT')
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OPS = {'<': 5, '>': 5, '=': 5, '>=': 5, '<=': 5, '<>': 5, 'IN': 8, 'AND': 11, 'OR': 12, 'NOT': 10, 'BETWEEN': 9, '(': 100, ')': 100}
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OPS = {'<': 5, '>': 5, '=': 5, '>=': 5, '<=': 5, '<>': 5, 'IN': 8, 'AND': 11, 'OR': 12, 'NOT': 10, 'BETWEEN': 9, '(': 1, ')': 1}
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def shunting_yard(token_list):
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output = []
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op_stack = []
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output = []
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op_stack = []
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# Basically takes in an infix notation calculation, converts it to a reverse polish notation where there is no
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# ambiguaty on which order operators are applied.
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while len(tokens2) > 0:
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token = tokens2.pop(0)
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# Basically takes in an infix notation calculation, converts it to a reverse polish notation where there is no
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# ambiguaty on which order operators are applied.
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while len(token_list) > 0:
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token = token_list.pop(0)
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if token == '(':
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op_stack.append(token)
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elif token == ')':
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while len(op_stack) > 0 and op_stack[-1] != '(':
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output.append(op_stack.pop())
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if len(op_stack) == 0:
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# No left paren on the stack, error
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raise Exception('Missing left paren')
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if token == '(':
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op_stack.append(token)
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elif token == ')':
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while len(op_stack) > 0 and op_stack[-1] != '(':
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output.append(op_stack.pop())
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lbracket = op_stack.pop()
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assert lbracket == '('
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# Pop off the left paren
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op_stack.pop()
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elif is_number(token):
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output.append(token)
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else:
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# Must be operator kw
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while len(op_stack) > 0 and OPS[op_stack[-1]] <= OPS[token]:
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output.append(op_stack.pop())
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op_stack.append(token)
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while len(op_stack) > 0:
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output.append(op_stack.pop())
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elif is_number(token):
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output.append(token)
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else:
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# Must be operator kw
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while len(op_stack) > 0 and OPS[op_stack[-1]] <= OPS[token]:
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output.append(op_stack.pop())
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op_stack.append(token)
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while len(op_stack) > 0:
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output.append(op_stack.pop())
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return output
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output = shunting_yard(tokens2)
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# Hacky funcition to convert dynamo functions (which are represented as lists) to their Class equivelent
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def to_func(val):
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@ -217,7 +237,11 @@ def get_filter_expression(expr, names, values):
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else:
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stack.append(to_func(token))
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return stack[0]
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result = stack.pop(0)
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if len(stack) > 0:
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raise ValueError('Malformed filter expression')
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return result
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class Op(object):
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@ -249,7 +273,7 @@ class Op(object):
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rhs = self.rhs
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if isinstance(self.rhs, (Op, Func)):
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rhs = self.rhs.expr(item)
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elif isinstance(self.lhs, six.string_types):
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elif isinstance(self.rhs, six.string_types):
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try:
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rhs = item.attrs[self.rhs].cast_value
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except Exception:
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@ -357,15 +381,6 @@ class OpIn(Op):
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return lhs in rhs
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class OpBetween(Op):
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OP = 'BETWEEN'
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def expr(self, item):
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lhs = self._lhs(item)
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rhs = self._rhs(item)
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return rhs[0] <= lhs <= rhs[1]
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class FuncAttrExists(Func):
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FUNC = 'attribute_exists'
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@ -432,18 +447,32 @@ class FuncSize(Func):
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def expr(self, item):
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if self.attr not in item.attrs:
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raise ValueError('Invalid option')
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raise ValueError('Invalid attribute name {0}'.format(self.attr))
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if item.attrs[self.attr].type in ('S', 'SS', 'NS', 'B', 'BS', 'L', 'M'):
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return len(item.attrs[self.attr].value)
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raise ValueError('Invalid option')
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raise ValueError('Invalid filter expression')
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class FuncBetween(Func):
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FUNC = 'between'
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def __init__(self, attribute, start, end):
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self.attr = attribute
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self.start = start
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self.end = end
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def expr(self, item):
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if self.attr not in item.attrs:
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raise ValueError('Invalid attribute name {0}'.format(self.attr))
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return self.start <= item.attrs[self.attr].cast_value <= self.end
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OP_CLASS = {
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'AND': OpAnd,
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'OR': OpOr,
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'IN': OpIn,
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'BETWEEN': OpBetween,
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'<': OpLessThan,
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'>': OpGreaterThan,
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'<=': OpLessThanOrEqual,
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@ -458,5 +487,6 @@ FUNC_CLASS = {
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'attribute_type': FuncAttrType,
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'begins_with': FuncBeginsWith,
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'contains': FuncContains,
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'size': FuncSize
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'size': FuncSize,
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'between': FuncBetween
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}
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@ -439,13 +439,22 @@ class DynamoHandler(BaseResponse):
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exclusive_start_key = self.body.get('ExclusiveStartKey')
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limit = self.body.get("Limit")
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items, scanned_count, last_evaluated_key = dynamodb_backend2.scan(name, filters,
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limit,
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exclusive_start_key,
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filter_expression,
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expression_attribute_names,
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expression_attribute_values)
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try:
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items, scanned_count, last_evaluated_key = dynamodb_backend2.scan(name, filters,
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limit,
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exclusive_start_key,
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filter_expression,
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expression_attribute_names,
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expression_attribute_values)
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except ValueError as err:
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er = 'com.amazonaws.dynamodb.v20111205#ValidationError'
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return self.error(er, 'Bad Filter Expression: {0}'.format(err))
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except Exception as err:
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er = 'com.amazonaws.dynamodb.v20111205#InternalFailure'
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return self.error(er, 'Internal error. {0}'.format(err))
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# Items should be a list, at least an empty one. Is None if table does not exist.
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# Should really check this at the beginning
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if items is None:
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er = 'com.amazonaws.dynamodb.v20111205#ResourceNotFoundException'
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return self.error(er, 'Requested resource not found')
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