Spreadsheet: safer formula evaluation
This commit is contained in:
Yorik van Havre
parent
1e1786fd41
commit
b4618e3b0a
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@ -24,6 +24,176 @@ import re, math, FreeCAD, FreeCADGui
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from PyQt4 import QtCore,QtGui
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DEBUG = True # set to True to show debug messages
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class MathParser:
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"A math expression parser"
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# code borrowed from http://www.nerdparadise.com/tech/python/parsemath/
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def __init__(self, string, vars={}):
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self.string = string
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self.index = 0
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self.vars = {
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'pi' : math.pi,
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'e' : math.e
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}
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for var in vars.keys():
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if self.vars.get(var) != None:
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raise Exception("Cannot redefine the value of " + var)
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self.vars[var] = vars[var]
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def getValue(self):
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value = self.parseExpression()
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self.skipWhitespace()
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if self.hasNext():
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raise Exception(
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"Unexpected character found: '" +
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self.peek() +
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"' at index " +
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str(self.index))
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return value
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def peek(self):
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return self.string[self.index:self.index + 1]
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def hasNext(self):
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return self.index < len(self.string)
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def skipWhitespace(self):
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while self.hasNext():
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if self.peek() in ' \t\n\r':
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self.index += 1
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else:
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return
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def parseExpression(self):
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return self.parseAddition()
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def parseAddition(self):
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values = [self.parseMultiplication()]
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while True:
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self.skipWhitespace()
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char = self.peek()
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if char == '+':
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self.index += 1
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values.append(self.parseMultiplication())
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elif char == '-':
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self.index += 1
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values.append(-1 * self.parseMultiplication())
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else:
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break
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return sum(values)
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def parseMultiplication(self):
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values = [self.parseParenthesis()]
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while True:
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self.skipWhitespace()
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char = self.peek()
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if char == '*':
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self.index += 1
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values.append(self.parseParenthesis())
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elif char == '/':
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div_index = self.index
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self.index += 1
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denominator = self.parseParenthesis()
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if denominator == 0:
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raise Exception(
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"Division by 0 kills baby whales (occured at index " +
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str(div_index) +
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")")
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values.append(1.0 / denominator)
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else:
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break
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value = 1.0
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for factor in values:
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value *= factor
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return value
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def parseParenthesis(self):
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self.skipWhitespace()
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char = self.peek()
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if char == '(':
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self.index += 1
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value = self.parseExpression()
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self.skipWhitespace()
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if self.peek() != ')':
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raise Exception(
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"No closing parenthesis found at character "
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+ str(self.index))
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self.index += 1
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return value
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else:
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return self.parseNegative()
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def parseNegative(self):
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self.skipWhitespace()
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char = self.peek()
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if char == '-':
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self.index += 1
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return -1 * self.parseParenthesis()
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else:
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return self.parseValue()
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def parseValue(self):
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self.skipWhitespace()
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char = self.peek()
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if char in '0123456789.':
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return self.parseNumber()
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else:
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return self.parseVariable()
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def parseVariable(self):
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self.skipWhitespace()
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var = ''
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while self.hasNext():
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char = self.peek()
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if char.lower() in '_abcdefghijklmnopqrstuvwxyz0123456789':
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var += char
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self.index += 1
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else:
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break
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value = self.vars.get(var, None)
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if value == None:
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raise Exception(
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"Unrecognized variable: '" +
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var +
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"'")
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return float(value)
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def parseNumber(self):
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self.skipWhitespace()
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strValue = ''
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decimal_found = False
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char = ''
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while self.hasNext():
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char = self.peek()
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if char == '.':
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if decimal_found:
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raise Exception(
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"Found an extra period in a number at character " +
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str(self.index) +
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". Are you European?")
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decimal_found = True
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strValue += '.'
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elif char in '0123456789':
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strValue += char
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else:
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break
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self.index += 1
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if len(strValue) == 0:
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if char == '':
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raise Exception("Unexpected end found")
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else:
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raise Exception(
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"I was expecting to find a number at character " +
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str(self.index) +
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" but instead I found a '" +
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char +
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"'. What's up with that?")
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return float(strValue)
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class Spreadsheet(object):
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"""An object representing a spreadsheet. Can be used as a
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FreeCAD object or as a standalone python object.
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@ -78,23 +248,11 @@ class Spreadsheet(object):
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if key.lower() in self._cells:
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key = key.lower()
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if self.isFunction(self._cells[key]):
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#print "result = ",self.getFunction(key)
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# building a list of safe functions allowed in eval
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safe_list = ['acos', 'asin', 'atan', 'atan2', 'ceil',
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'cos', 'cosh', 'e', 'exp', 'fabs',
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'floor', 'fmod', 'frexp', 'hypot', 'ldexp', 'log',
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'log10', 'modf', 'pi', 'pow', 'radians', 'sin',
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'sinh', 'sqrt', 'tan', 'tanh']
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tools = dict((k, getattr(math, k)) for k in safe_list)
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# adding abs
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tools["abs"] = abs
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# removing all builtins from allowed functions
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tools["__builtins__"] = None
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try:
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e = eval(self._format(key),tools,{"self":self})
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try:
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e = self.evaluate(key)
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except:
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if DEBUG: print "Error evaluating formula"
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return self._cells[key]
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print "Error evaluating formula"
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return None
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else:
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return e
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else:
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@ -123,18 +281,6 @@ class Spreadsheet(object):
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if self.isFunction(key):
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self._updateDependencies(key)
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def _format(self,key):
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"formats all cellnames in the function a the given cell"
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elts = re.split(r'(\W+)',self._cells[key][1:])
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#print elts
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result = ''
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for e in elts:
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if self.isKey(e):
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result += "self."+e
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else:
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result += e
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return result
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def _updateDependencies(self,key,value=None):
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"search for ancestors in the value and updates the table"
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ancestors = []
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@ -162,6 +308,17 @@ class Spreadsheet(object):
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return True
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else:
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return False
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def isNumeric(self,key):
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"isNumeric(cell): returns True if the given cell returns a number"
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if self.isFunction(key):
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res = self.evaluate(key)
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else:
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res = self._cells[key]
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if isinstance(res,float) or isinstance(res,int):
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return True
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else:
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return False
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def isKey(self,value):
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"isKey(val): returns True if the given value is a valid cell number"
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@ -222,6 +379,31 @@ class Spreadsheet(object):
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if index in [c,r]:
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cells[k] = self._cells[k]
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return cells
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def evaluate(self,key):
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"evaluate(key): evaluates the given formula"
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elts = re.split(r'(\W+)',self._cells[key][1:])
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result = ""
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for e in elts:
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if self.isKey(e):
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if self.isFunction(e):
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if self.isNumeric(e):
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result += str(self.evaluate(e))
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else:
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print "Error evaluating formula"
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return
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elif self.isNumeric(e):
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result += str(self._cells[e])
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else:
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result += e
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print "Evaluating ",result
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try:
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p = MathParser(result)
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result = p.getValue()
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except Exception as (ex):
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msg = ex.message
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raise Exception(msg)
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return result
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class ViewProviderSpreadsheet(object):
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