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Commit d0fc453

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‎CH8/Checkpoints

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#8.1
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(a) True
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(b) 3
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(c) True
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(d) True
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(e) True
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(f) False
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(g) True
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(h) WELCOME TO PYTHON
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(i) 8
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(j) o
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(k) ome
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(l) totototo
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(m) 17
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(n) y
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(o) (whitespace character)
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(p) t
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(q) welcome to python
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(r) 15
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(s) False
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(t) False
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(u) False
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(v) Welcome to PythonWelcome to Python
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#8.2
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All of them are correct statements except the statement
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"s3 = s1 - s2" because '-' is not defined over strings.
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#8.3
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Welcome to Python
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Welcabcme tabc Pythabcn
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#8.4
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(a) isEqual = (s1 == s2)
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(b) isEqual = (s1.lower() == s2.lower())
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(c) b = s1.startswith('AAA')
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(d) b = s1.endswith("AAA")
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(e) x = len(s1)
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(f) x = s1[0]
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(g) s3 = s1+s2
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(h) s3 = s1[1:]
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(i) s3 = s1[1:5]
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(j) s3 = s1.lower()
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(k) s3 = s1.upper()
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(l) s3 = s1.strip()
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(m) s3 = s1.replace('e','E')
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(n) x = s1.find('e')
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(o) x = s1.rfind('abc')
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#8.5
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No. The string object is immutable.
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#8.6
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0
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#8.7
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s.islower() or s.isupper()
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#8.8
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s.isalpha()
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#8.9
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Defining methods for operators is called operator overloading.
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Operator overloading allows the programmer to use the
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built-in operators for user-defined methods.
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#8.10
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+: __add__(self, other)
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-: __sub__(self, other)
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*: __mul__(self, other)
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/: __truediv__(self, other)
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%: __mod__(self, other)
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==: __eq__(self, other)
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!=: __ne__(self, other)
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<: __lt__(self, other)
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<=: __le__(self, other)
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>: __gt__(self, other)
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>=: __ge__(self, other)
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#8.11
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Yes.
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#8.12
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Yes.

‎CH8/EX8.1.py

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# 8.1 (Check SSN) Write a program that prompts the user to enter a Social Security
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# number in the format ddd-dd-dddd, where d is a digit. The program displays
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# Valid SSN for a correct Social Security number or Invalid SSN otherwise.
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ssn = input("Enter your social security number (ddd-dd-dddd): ")
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s1 = ssn[0:3]
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s2 = ssn[4:6]
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s3 = ssn[7:11]
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if (len(s1)+len(s2)+len(s3) == 9) and s1.isdigit() and s2.isdigit() and s3.isdigit():
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print("SSN is valid")
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else:
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print("SSN is not valid")

‎CH8/EX8.10.py

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# 8.10 (Decimal to binary) Write a function that parses a decimal number into a binary
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# number as a string. Use the function header:
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# def decimalToBinary(value):
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# Write a test program that prompts the user to enter a decimal integer value and displays
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# the corresponding binary value.
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def decimalToBinary(value):
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bin = ''
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while value > 0:
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if value % 2 == 0:
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bin = bin + '0'
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else:
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bin = bin + '1'
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value = value // 2
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bin = bin[::-1]
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return bin
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def main():
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val = eval(input("Enter a decimal: "))
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bin = decimalToBinary(val)
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print(bin)
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main()

‎CH8/EX8.11.py

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# 8.11 (Reverse a string) Write a function that reverses a string. The header of the function
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# is:
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# def reverse(s):
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# Write a test program that prompts the user to enter a string, invokes the reverse
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# function, and displays the reversed string.
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def reverse(s):
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new = s[len(s):0:-1] + s[0]
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return new
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def main():
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st = input("Enter a string: ")
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print("The reverse of", st, "is", reverse(st))
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main()

‎CH8/EX8.12.py

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# 8.12 (Bioinformatics: find genes) Biologists use a sequence of letters A, C, T, and G to
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# model a genome. A gene is a substring of a genome that starts after a triplet ATG
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# and ends before a triplet TAG, TAA, or TGA. Furthermore, the length of a gene
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# string is a multiple of 3 and the gene does not contain any of the triplets ATG, TAG,
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# TAA, and TGA. Write a program that prompts the user to enter a genome and displays
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# all genes in the genome. If no gene is found in the input sequence, the program
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# displays no gene is found.
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def findGen(genome):
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found = False
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for i in range(len(genome)):
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startInd = str(genome).find("ATG")
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if startInd == -1:
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break
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endInd1, endInd2, endInd3 = \
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str(genome).find("TAG"), str(genome).find("TAA"), str(genome).find("TGA")
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if endInd1 == -1:
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endInd1 = len(genome) * 2
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if endInd2 == -1:
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endInd2 = len(genome) * 2
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if endInd3 == -1:
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endInd3 = len(genome) * 2
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endInd = min(endInd1, endInd2, endInd3)
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gen = str(genome)[startInd + 3:endInd]
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if len(gen) % 3 == 0:
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print(gen)
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found = True
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genome = genome[endInd + 3:len(genome)]
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if not found:
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print("No genes found")
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def main():
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g = input("Enter a genome string: ")
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findGen(g)
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main()

‎CH8/EX8.13.py

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# 8.13 (Longest common prefix) Write a method that returns the longest common prefix
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# of two strings. For example, the longest common prefix of distance and
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# disinfection is dis. The header of the method is:
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# def prefix(s1, s2)
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# If the two strings have no common prefix, the method returns an empty string.
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# Write a main method that prompts the user to enter two strings and displays their
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# common prefix.
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def prefix(s1, s2):
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for i in range(len(s1)):
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s = s1[0:len(s1) - i]
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if str(s2).startswith(str(s)):
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return s
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return ""
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def main():
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s1, s2 = input("Enter two strings: ").split()
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print(prefix(s1, s2))
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main()

‎CH8/EX8.14.py

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# 8.14 (Financial: credit card number validation) Rewrite Exercise 6.29 using a string
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# input for a credit card number.
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def main():
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number = input("Enter a credit card number as a string: ").strip()
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if isValid(number):
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print(number + " is valid")
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else:
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print(number + " is invalid")
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# Return true if the card number is valid
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def isValid(number):
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return (number.startswith("4") or number.startswith("5") or
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number.startswith("6") or number.startswith("37")) and \
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(sumOfDoubleEvenPlace(number) + sumOfOddPlace(number)) % 10 == 0
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# Get the result from Step 2
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def sumOfDoubleEvenPlace(cardNumber):
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result = 0
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for i in range(len(cardNumber) - 2, -1, - 2):
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result += getDigit(int(cardNumber[i]) * 2)
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return result
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# Return this number if it is a single digit, otherwise, return
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# the sum of the two digits
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def getDigit(number):
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return number % 10 + (number // 10 % 10)
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# Return sum of odd place digits in number
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def sumOfOddPlace(cardNumber):
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result = 0
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for i in range(len(cardNumber) - 1, -1, -2):
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result += int(cardNumber[i])
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return result
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main()

‎CH8/EX8.15.py

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# 8.15 (Business: check ISBN-10) An ISBN-10 (International Standard Book Number)
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# consists of 10 digits:d1d2d3d4d5d6d7d8d9d10. The last digit, is a checksum,
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# which is calculated from the other nine digits using the following formula:
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# (d1 * 1 + d2 * 2 + d3 * 3 + d4 * 4 + d5 * 5
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# + d6 * 6 + d7 * 7 + d8 * 8 + d9 * 9) % 11
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# If the checksum is 10, the last digit is denoted as X, according to the ISBN convention.
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# Write a program that prompts the user to enter the first 9 digits as a string
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# and displays the 10-digit ISBN (including leading zeros). Your program should
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# read the input as a string.
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digits = input("Enter the first 9 digits of an ISBN-10 as a string: ")
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if digits.isdigit():
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lastDigit = 0
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for i in range(9):
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lastDigit += int(digits[i]) * (i+1)
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lastDigit = lastDigit % 11
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isbn = ''
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if lastDigit == 10:
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isbn = digits + 'X'
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else:
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isbn = digits + str(lastDigit)
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print("The ISBN-10 number is", isbn)
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else:
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print("incorrect input")

‎CH8/EX8.16.py

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# 8.16 (Business: check ISBN-13) ISBN-13 is a new standard for identifying books. It
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# uses 13 digits: d1d2d3d4d5d6d7d8d9d10d11d12d13. The last digit, is a checksum,
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# which is calculated from the other digits using the following formula:
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# 10 - (d1 + 3d2 + d3 + 3d4 + d5 + 3d6 + d7 + 3d8 + d9 + 3d10 + d11 + 3d12) % 10
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# If the checksum is 10, replace it with 0. Your program should read the input as a
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# string.
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digits = input("Enter the first 12 digits of an ISBN-13 as a string: ")
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checksum = 0
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for i in range(12):
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checksum += int(digits[i]) * (1 if i % 2 == 0 else 3)
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checksum = 10 - checksum % 10
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if checksum == 10:
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digits += '0'
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else:
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digits += str(checksum)
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print("The ISBN-13 number is", digits)

‎CH8/EX8.17.py

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# 8.17 (The Point class) Design a class named Point to represent a point with x- and ycoordinates.
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# The class contains:
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# ■しかく Two private data fields x and y that represent the coordinates with get methods.
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# ■しかく A constructor that constructs a point with specified coordinates with default
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# point (0, 0).
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# ■しかく A method named distance that returns the distance from this point to another
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# point of the Point type.
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# ■しかく A method named isNearBy(p1) that returns true if point p1 is close to this
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# point. Two points are close if their distance is less than 5.
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# ■しかく Implement the __str__ method to return a string in the form (x, y).
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# Draw the UML diagram for the class, and then implement the class. Write a test
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# program that prompts the user to enter two points, displays the distance between
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# them, and indicates whether they are near each other.
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import math
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class Point:
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def __init__(self, x=0, y=0):
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self.__x__ = x
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self.__y__ = y
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def getX(self):
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return self.__x__
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def getY(self):
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return self.__y__
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def distance(self, point):
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dis = math.sqrt((self.__x__ - point.getX()) ** 2 + (self.__y__ - point.getY()) ** 2)
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return dis
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def isNearBy(self, point):
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d = self.distance(point)
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return True if d < 5 else False
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def __str__(self):
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return '( ' + str(self.__x__) + ',' + str(self.__y__) + ' )'
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def main():
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x1, y1, x2, y2 = eval(input("Enter two points x1, y1, x2, y2: "))
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p1 = Point(x1, y1)
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p2 = Point(x2, y2)
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print("The distance between the two points is", p1.distance(p2))
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if p1.isNearBy(p2):
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print("The two points are near each other")
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else:
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print("The two points are not near each other")
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main()

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