Section 3: The AdvancedCalculator class

_isVariable(self, word) (5 points) Determines if the input is a valid variable name (see above for rules for names). The string methods str.isalpha()and str.isalnum()could be helpful here.

Input (excluding self)
str	word	The string to check if it is a valid variable name

Output
bool	True if word is a variable name, False otherwise

_replaceVariables(self, expr) (10 points) Replaces all variables in the input expression with the current value of those variables saved in self.states.

Input (excluding self)
str	expr	The input expression that may contain variables

Output
str	The expression with all variables replaced with their values
None	Nothing is returned if expression has invalid variables or uses a variable that has not been defined

calculateExpressions(self) (15 points)

Evaluates each expression saved in self.expressions. For each line, replace all variables in the expression with their values, then use a Calculator object to evaluate the expression and update self.states. This method returns a dictionary that shows the progression of the calculations, with the key being the line evaluated and the value being the current state of self.states after that line is evaluated. The dictionary must include a key named '_return_' with the return value as its value.

Hint: the str.split(sep)method can be helpful for separating lines, as well as separating the variable from the expression (for the lines that are formatted as var = expr). The str.strip()method removes the white space before and after a string. Don't forget dictionaries are mutable objects!

>>> 'hi;there'.split(';') ['hi', 'there']

>>> 'hi=there'.split('=')

['hi', 'there']

>>> ' hi there '.strip()

' hi there'

Output
dict	The different states of self.states as the calculation progresses.
None	Nothing is returned if there was an error replacing variables

class AdvancedCalculator:

'''

>>> C = AdvancedCalculator()

>>> C.states == {}

True

>>> C.setExpression('a = 5;b = 7 + a;a = 7;c = a + b;c = a * 0;return c')

>>> C.calculateExpressions() == {'a = 5': {'a': 5.0}, 'b = 7 + a': {'a': 5.0, 'b': 12.0}, 'a = 7': {'a': 7.0, 'b': 12.0}, 'c = a + b': {'a': 7.0, 'b': 12.0, 'c': 19.0}, 'c = a * 0': {'a': 7.0, 'b': 12.0, 'c': 0.0}, '_return_': 0.0}

True

>>> C.states == {'a': 7.0, 'b': 12.0, 'c': 0.0}

True

>>> C.setExpression('x1 = 5;x2 = 7 * ( x1 - 1 );x1 = x2 - x1;return x2 + x1 ^ 3')

>>> C.states == {}

True

>>> C.calculateExpressions() == {'x1 = 5': {'x1': 5.0}, 'x2 = 7 * ( x1 - 1 )': {'x1': 5.0, 'x2': 28.0}, 'x1 = x2 - x1': {'x1': 23.0, 'x2': 28.0}, '_return_': 12195.0}

True

>>> print(C.calculateExpressions())

{'x1 = 5': {'x1': 5.0}, 'x2 = 7 * ( x1 - 1 )': {'x1': 5.0, 'x2': 28.0}, 'x1 = x2 - x1': {'x1': 23.0, 'x2': 28.0}, '_return_': 12195.0}

>>> C.states == {'x1': 23.0, 'x2': 28.0}

True

>>> C.setExpression('x1 = 5 * 5 + 97;x2 = 7 * ( x1 / 2 );x1 = x2 * 7 / x1;return x1 * ( x2 - 5 )')

>>> C.calculateExpressions() == {'x1 = 5 * 5 + 97': {'x1': 122.0}, 'x2 = 7 * ( x1 / 2 )': {'x1': 122.0, 'x2': 427.0}, 'x1 = x2 * 7 / x1': {'x1': 24.5, 'x2': 427.0}, '_return_': 10339.0}

True

>>> C.states == {'x1': 24.5, 'x2': 427.0}

True

>>> C.setExpression('A = 1;B = A + 9;C = A + B;A = 20;D = A + B + C;return D - A')

>>> C.calculateExpressions() == {'A = 1': {'A': 1.0}, 'B = A + 9': {'A': 1.0, 'B': 10.0}, 'C = A + B': {'A': 1.0, 'B': 10.0, 'C': 11.0}, 'A = 20': {'A': 20.0, 'B': 10.0, 'C': 11.0}, 'D = A + B + C': {'A': 20.0, 'B': 10.0, 'C': 11.0, 'D': 41.0}, '_return_': 21.0}

True

>>> C.states == {'A': 20.0, 'B': 10.0, 'C': 11.0, 'D': 41.0}

True

>>> C.setExpression('A = 1;B = A + 9;2C = A + B;A = 20;D = A + B + C;return D + A')

>>> C.calculateExpressions() is None

True

>>> C.states == {}

True

'''

def __init__(self):

self.expressions = ''

self.states = {}

def setExpression(self, expression):

self.expressions = expression

self.states = {}

def _isVariable(self, word):

'''

>>> C = AdvancedCalculator()

>>> C._isVariable('volume')

True

>>> C._isVariable('4volume')

False

>>> C._isVariable('volume2')

True

>>> C._isVariable('vol%2')

False

'''

# YOUR CODE STARTS HERE

pass

def _replaceVariables(self, expr):

'''

>>> C = AdvancedCalculator()

>>> C.states = {'x1': 23.0, 'x2': 28.0}

>>> C._replaceVariables('1')

'1'

>>> C._replaceVariables('105 + x')

>>> C._replaceVariables('7 * ( x1 - 1 )')

'7 * ( 23.0 - 1 )'

>>> C._replaceVariables('x2 - x1')

'28.0 - 23.0'

'''

# YOUR CODE STARTS HERE

pass

def calculateExpressions(self):

self.states = {}

calcObj = Calculator() # method must use calcObj to compute each expression

# YOUR CODE STARTS HERE

pass