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(Python)Ok so I have to make a code to create def calculator(expr): after I complete following defintions def findNextOpr(txt): def...
P.S instruction is given below too, after my code.
< I JUST NEED HELP FOR THE LAST PART >
Codes that I completed are given below
def findNextOpr(txt):
if len(txt)<= 0 or not isinstance(txt,str):
return "type error: findNextOpr"
operators = "+-*/"
num = "' ' 0123456789"
x = 0
while len(txt) > 0:
if txt[x:x+1] in operators:
return len(txt[0:x])
if x == len(txt) - 1:
return -1
x += 1
def isNumber(txt):
if not isinstance(txt, str):
return "type error: isNumber"
if len(txt)==0:
return False
if len(txt) > 0:
try:
float(txt)
return True
except:
ValueError
return False
def getNextNumber(expr, pos):
'''if len(expr)==0 or not isinstance(expr, str) or pos<0 or
pos>=len(expr) or not isinstance(pos, int):
return None, None, "type error: getNextNumber"'''
operators = "+-*/"
num = "0123456789"
space = " "
ans1 = ""
x = 0
y = 0
txt = expr[pos:len(expr)]
i = pos
while i < len(expr):
if expr[i] in operators:
break
elif expr[i] == space:
if ans1 == "":
j = i
while ans1 == "":
if expr[j] in operators:
break
if expr[j] in num:
ans1 += expr[j]
j += 1
i = j
else:
break
elif expr[i] in num or expr[i] == ".":
ans1 += expr[i]
i += 1
if isNumber(ans1) is True:
if "." not in ans1:
ans1 += ".0"
if ans1 == "":
ans1 = None
if findNextOpr(txt) == -1:
ans2 = None
ans3 = None
else:
ans2 = expr[pos + findNextOpr(txt)]
ans3 = pos + findNextOpr(txt)
return ans1, ans2, ans3
def exeOpr(num1, opr, num2):
if opr=="+":
return num1+num2
elif opr=="-":
return num1-num2
elif opr=="*":
return num1*num2
elif opr=="/":
return num1/num2
else:
return "error in exeOpr"
-------------------------------------- instruction--------------------------------------
def findNextOpr(txt):
"""
Takes a string and returns -1 if there is no operator in txt,
otherwise returns
the position of the leftmost operator. +, -, *, / are all the 4
operators
>>> findNextOpr(' 3* 4 - 5')
3
>>> findNextOpr('8 4 - 5')
6
>>> findNextOpr('89 4 5')
- 1
"""
if len(txt)<=0 or not isinstance(txt,str):
return "type error: findNextOpr"
# --- YOU CODE STARTS HERE
# --- CODE ENDS HERE
def isNumber(txt):
"""
Takes a string and returns True if txt is convertible to float,
False otherwise
>>> isNumber('1 2 3')
False
>>> isNumber('- 156.3')
False
>>> isNumber('29.99999999')
True
>>> isNumber(' 5.9999 ')
True
"""
if not isinstance(txt, str):
return "type error: isNumber"
if len(txt)==0:
return False
# --- YOU CODE STARTS HERE
# --- CODE ENDS HERE
def getNextNumber(expr, pos):
"""
expr is a given arithmetic formula of type string
pos is the start position in expr
1st returned value = the next number (None if N/A)
2nd returned value = the next operator (None if N/A)
3rd retruned value = the next operator position (None if N/A)
>>> getNextNumber('8 + 5 -2',0)
(8.0, '+', 3)
>>> getNextNumber('8 + 5 -2',4)
(5.0, '-', 13)
>>> getNextNumber('4.5 + 3.15 / 5',0)
(4.5, '+', 4)
>>> getNextNumber('4.5 + 3.15 / 5',10)
(None, '/', 19)
"""
if len(expr)==0 or not isinstance(expr, str) or pos<0 or
pos>=len(expr) or not isinstance(pos, int):
return None, None, "type error: getNextNumber"
# --- YOU CODE STARTS HERE
# --- CODE ENDS HERE
def exeOpr(num1, opr, num2):
#This function is just an utility function for calculator(expr). It is
skipping type check
if opr=="+":
return num1+num2
elif opr=="-":
return num1-num2
elif opr=="*":
return num1*num2
elif opr=="/":
return num1/num2
else:
return "error in exeOpr"
def calculator(expr):
"""
Takes a string and returns the calculated result if the
arithmethic expression is value,
and error message otherwise
>>> calculator(" -4 +3 -2")
- 3.0
>>> calculator("-4 +3 -2 / 2")
- 2.0
>>> calculator("-4 +3 - 8 / 2")
- 5.0
>>> calculator(" -4 + 3 - 8 / 2")
- 5.0
>>> calculator("23 / 12 - 223 + 5.25 * 4 * 3423")
71661.91666666667
>>> calculator("2 - 3*4")
- 10.0
>>> calculator("4++ 3 +2")
'error message'
>>> calculator("4 3 +2")
'input error line B: calculator'
"""
if len(expr)<=0 or not isinstance(expr,str): #Line A
return "input error line A: calculator"
# Concatenate '0' at he beginning of the expression if it starts with
a negative number to get '-' when calling getNextNumber
# "-2.0 + 3 * 4.0 â
becomes "0-2.0 + 3 * 4.0 â
.
expr=expr.strip()
if expr[0]=="-":
expr = "0 " + expr
newNumber, newOpr, oprPos = getNextNumber(expr, 0)
# Initialization. Holding two modes for operator precedence:
"addition" and "multiplication"
if newNumber is None: #Line B
return "input error line B: calculator"
elif newOpr is None:
return newNumber
elif newOpr=="+" or newOpr=="-":
mode="add"
addResult=newNumber #value so far in the addition mode
elif newOpr=="*" or newOpr=="/":
mode="mul"
addResult=0
mulResult=newNumber #value so far in the mulplication mode
addLastOpr = "+"
pos=oprPos+1 #the new current position
opr=newOpr #the new current operator
#Calculation starts here, get next number-operator and perform case
analysis. Conpute values using exeOpr
while True:
# --- YOU CODE STARTS HERE
# --- CODE ENDS HERE
