Solutions

Author: OmarAlmighty

CH12/EX12.1.py

@@ -61,7 +61,7 @@ def getSide2(self):
         return self.side2
 
     def setSide2(self, side2):
-        self.side1 = side2
+        self.side2 = side2
 
     def getSide3(self):
         return self.side3

CH13/Checkpoints

@@ -0,0 +1,119 @@
+#13.1
+For reading: open(filename,'r')
+For writing: open(filename,'w')
+For appending: open(filename,'a')
+
+#13.2
+The file name string must has prefix r or with double backslash:
+r"c:\book\test.txt"
+or, "c:\\book\\test.txt"
+
+#13.3
+A runtime error will be thrown.
+The current file content will overwritten.
+
+#13.4
+os.path.isfile(filename)
+
+#13.5
+filename.read(30)
+
+#13.6
+s = filename.read()
+
+#13.7
+filename.readline()
+
+#13.8
+lines = filename.readlines()
+
+#13.9
+No, it will return ''
+
+#13.10
+If the read function returns ''
+
+#13.11
+filename.write(data)
+
+#13.12
+Using repr function. Or, using notation r"string".
+
+#13.13
+To write numeric data, write them as strings separated by spaces.
+To read the numeric data, read the data, split them by spaces, and evaluate numbers values
+
+#13.14
+filenameforReading = askopenfilename()
+
+#13.15
+filenameforWriting = asksaveasfilename()
+
+#13.16
+infile = urllib.request.urlopen(url)
+
+#13.17
+decode()
+
+#13.18
+1) Will statement3 be executed? NO
+2) If the exception is not caught, will statement4 be executed? NO
+3) If the exception is caught in the except block, will statement4 be executed? YES
+
+#13.19
+Index out of bound
+
+#13.20
+Divided by zero!
+
+#13.21
+Index out of bound
+
+#13.22
+1) Will statement5 be executed if the exception is not caught? NO
+2) If the exception is of type Exception3, will statement4 be executed, and will
+statement5 be executed? YES, both will be executed
+
+#13.23
+raise ExceptionClass()
+
+#13.24
+1) Preventing the program from terminating abnormally.
+2) Informing the user that he/she may made an error.
+3) The essential benefit of exception handling is to separate the detection of an error (done in a called function)
+   from the handling of an error (done in the calling method).
+
+#13.25
+Done
+Nothing is wrong
+Finally we are here
+Continue
+
+#13.26
+Index out of bound
+Finally we are here
+Continue
+
+#13.27
+ArithmeticError class is super class of ZeroDivisionError,
+So ZeroDivisionError should be placed before ArithmeticError
+
+#13.28
+You can define a custom exception class by extending BaseException or a subclass
+of BaseException.
+
+#13.29
+For writing: file = open(filename, "wb")
+For reading: file = open(filename, "rb")
+
+#13.30
+To write an object: pickle.dump(data, filename)
+To read an object:  pickle.load(filename)
+
+#13.31
+The file is closed in the finally clause after pickle.load(infile) is executed,
+even though the end of file is not reached.
+
+#13.32
+Yes.
+

CH13/EX13.1.py

@@ -0,0 +1,17 @@
+# 13.1 (Remove text) Write a program that removes all the occurrences of a specified
+# string from a text file. Your program should prompt the user to enter a filename
+# and a string to be removed.
+
+filename = input("Enter a filename: ").strip()
+string = input("Enter the string to be removed: ")
+file = open(filename, 'r')
+data = ''
+for line in file:
+    data += line.replace(string, '')
+
+
+# I will create a new file instead of writing on the same file for future exercises usage.
+resFile = open('result', 'w')
+resFile.write(data)
+resFile.close()
+print("Done")

CH13/EX13.10.py

@@ -0,0 +1,111 @@
+# 13.10 (The Rational class) Modify the Rational class in Listing 8.4, Rational.py, to
+# throw a RuntimeError exception if the denominator is 0.
+
+
+class Rational:
+    def __init__(self, numerator=0, denominator=1):
+        if denominator == 0:
+            raise RuntimeError()
+
+        divisor = gcd(numerator, denominator)
+        self.__numerator = (1 if denominator > 0 else -1) \
+                           * int(numerator / divisor)
+        self.__denominator = int(abs(denominator) / divisor)
+
+    # Add a rational number to this rational number
+    def __add__(self, secondRational):
+        n = self.__numerator * secondRational[1] + \
+            self.__denominator * secondRational[0]
+        d = self.__denominator * secondRational[1]
+        return Rational(n, d)
+
+    # Subtract a rational number from this rational number
+    def __sub__(self, secondRational):
+        n = self.__numerator * secondRational[1] - \
+            self.__denominator * secondRational[0]
+        d = self.__denominator * secondRational[1]
+        return Rational(n, d)
+
+    # Multiply a rational number to this rational
+    def __mul__(self, secondRational):
+        n = self.__numerator * secondRational[0]
+        d = self.__denominator * secondRational[1]
+        return Rational(n, d)
+
+    # Divide a rational number by this rational number
+    def __truediv__(self, secondRational):
+        n = self.__numerator * secondRational[1]
+        d = self.__denominator * secondRational[0]
+        return Rational(n, d)
+
+    # Return a float for the rational number
+    def __float__(self):
+        return self.__numerator / self.__denominator
+
+        # Return an integer for the rational number
+
+    def __int__(self):
+        return int(self.__float__())
+
+    # Return a string representation
+    def __str__(self):
+        if self.__denominator == 1:
+            return str(self.__numerator)
+        else:
+            return str(self.__numerator) + "/" + str(self.__denominator)
+
+    def __lt__(self, secondRational):
+        return self.__cmp__(secondRational) < 0
+
+    def __le__(self, secondRational):
+        return self.__cmp__(secondRational) <= 0
+
+    def __gt__(self, secondRational):
+        return self.__cmp__(secondRational) > 0
+
+    def __ge__(self, secondRational):
+        return self.__cmp__(secondRational) >= 0
+
+    # Compare two numbers
+    def __cmp__(self, secondRational):
+        temp = self.__sub__(secondRational)
+        if temp[0] > 0:
+            return 1
+        elif temp[0] < 0:
+            return -1
+        else:
+            return 0
+
+            # Return numerator and denominator using an index operator
+
+    def __getitem__(self, index):
+        if index == 0:
+            return self.__numerator
+        else:
+            return self.__denominator
+
+
+def gcd(n, d):
+    n1 = abs(n)
+    n2 = abs(d)
+    gcd = 1
+
+    k = 1
+    while k <= n1 and k <= n2:
+        if n1 % k == 0 and n2 % k == 0:
+            gcd = k
+        k += 1
+
+    return gcd
+
+
+def main():
+    try:
+        n1 = Rational(5, 10)
+        n2 = Rational(1, 0)
+        print(n1 + n2)
+    except RuntimeError:
+        print("Cannot divide by Zero!")
+
+
+main()

CH13/EX13.11.py

@@ -0,0 +1,89 @@
+# 13.11 (The Triangle class) Modify the Triangle class in Programming Exercise 12.1
+# to throw a RuntimeError exception if the three given sides cannot form a
+# triangle.
+
+import math
+
+
+class GeometricObject:
+    def __init__(self, color="green", filled=True):
+        self.__color = color
+        self.__filled = filled
+
+    def getColor(self):
+        return self.__color
+
+    def setColor(self, color):
+        self.__color = color
+
+    def isFilled(self):
+        return self.__filled
+
+    def setFilled(self, filled):
+        self.__filled = filled
+
+    def __str__(self):
+        return "color: " + self.__color + \
+               " and filled: " + str(self.__filled)
+
+
+class Triangle(GeometricObject):
+    def __init__(self, side1=1.0, side2=1.0, side3=1.0, color="green", isFilld=True):
+        super().__init__(color, isFilld)
+        self.__side1 = side1
+        self.__side2 = side2
+        self.__side3 = side3
+        if not self.isLegal():
+            raise RuntimeError()
+
+    def isLegal(self):
+        return self.__side1 + self.__side2 > self.__side3 and \
+               self.__side2 + self.__side3 > self.__side1 and \
+               self.__side1 + self.__side3 > self.__side2
+
+    def getSide1(self):
+        return self.__side1
+
+    def setSide1(self, side1):
+        self.__side1 = side1
+
+    def getSide2(self):
+        return self.__side2
+
+    def setSide2(self, side2):
+        self.__side2 = side2
+
+    def getSide3(self):
+        return self.__side3
+
+    def setSide3(self, side3):
+        self.__side3 = side3
+
+    def getArea(self):
+        s = (self.__side1 + self.__side2 + self.__side3) / 2
+        area = math.sqrt(s * (s - self.__side1) * (s - self.__side2) * (s - self.__side3))
+        return area
+
+    def getPerimeter(self):
+        return self.__side1 + self.__side2 + self.__side3
+
+    def __str__(self):
+        return super().__str__() + " Triangle: side1 = " + str(self.__side1) + " side2 = " + \
+               str(self.__side2) + " side3 = " + str(self.__side3)
+
+
+def main():
+    try:
+        s1, s2, s3 = eval(input("Enter three sides of a Triangle: "))
+        color = input("Enter color of a triangle: ")
+        isFilled = bool(int(input("Is the triangle filled? (1 or 0): ")))
+
+        trngl = Triangle(s1, s2, s3, color, isFilled)
+        print("Triangle's area is:", trngl.getArea())
+        print("Triangle's perimeter is:", trngl.getPerimeter())
+        print(trngl)
+    except RuntimeError:
+        print("Cannot form a triangle")
+
+
+main()