Python day 1 recap

Question sheets

Page 1

1.) Option 1 and 2, option 3 is wrong (Python will see this as three variables with names enter, your and name separated by spaces - this gives a syntax error)

2.) Option 1, 3, 4 and 5. Option 2 is wrong - Python can't make an integer out of letters.

3.) Option 1 and 4. Option 2 is wrong - you cannot assign a value to an integer (it cannot be a variable name), option 3 is also wrong - when you assign the variable has to be on the left of the = sign.

4.) Option 1 and 4. Option 2 is wrong, you cannot use ., and option 3 is a command - you cannot make this a variable.

5.) Option 1, 2 and 3. Option 4 is a division by zero.

6.) Option 1 and 2 will result in an integer 8 (the // is the same as /), option 4 will result in a float 8.0, and option 3 will result in 16.

7.) Option 2 is the only 'real' comment - you can use option 1 as a comment but it's also a multi-line string. Option 3 will fail, option 4 is a string.

Page 2

• 1023 - int
• None - NoneType
• [2, 4, 8, 16] - list
• True - Boolean
• 17.54 - float
• ('Roger',1952) - tuple
• "my fat cat" - str(ing)
• {'name': 'Roger', 'birth': 1952} - dict(ionary)

Page 3

Starting from top, clockwise:

• False
• my fat rat
• 3
• cat
• my fat cat (NOTE: no newline!)
• MY FAT CAT
• t
• ['my','fat','cat']

Page 4

• 1 -> R.GB
• 2 -> 3. RGB
• 3 -> 3.14
• 4 -> B RG
• 5 -> 5
• 6 -> RG 7B

Page 5

Starting from top, clockwise:

• [0,1]
• 1
• [0,0,1,2]
• 0 (Note: default is to take last from list)
• 4
• True
• [2,0,1,0,"A"]
• 2

Page 6

Operations in order:

5, 1, 2, 4, 3

Page 7

Operations in order:

3, 5, 1, 6, 2, 4

Page 8

1.) Option 3

2.) Option 2. Option 1 multiplies the list, option 3 starts at 0, option 4 gives the wrong values (8 at the end)

1.) Options 1 and 3. In option 2 there's a comma missing, option 4 is a list

2.) Options 1 and 3.

3.) Options 1, 2, 3, and 4

Page 9

1.) Options 2, 3, 4 and 6. Option 1 is an assignment, 5 is missing :.

2.) Options 1, 2, 3.

3.) Options 1, 3.

4.) Options 1, 2, 3. Option 6 is correct if seq is a list/tuple/string

5.) Options 1, 2, 4, 5, 6

Page 10

• 1 -> a != 0
• 2 -> a < 19
• 3 -> abs(a) < 7
• 4 -> a >= 0

Exercise solution

# This variable will be used for the while loop
validSequence = False
 
# Keep on going as long as the DNA sequence is not valid
while not validSequence:
 
  # Get a string from the user
  fullDnaSequence = input("Please enter your full DNA sequence:")
  fullDnaSequence = fullDnaSequence.upper()
 
  # Count the GACT characters in the sequence
  gactCount = 0
  for code in 'GACT':
    gactCount += fullDnaSequence.count(code)
 
  # Check if the number of GACT characters matches the full length of the sequence
  # and set validSequence to True if so - this will stop the while: loop
  if gactCount == len(fullDnaSequence):
    validSequence = True
  else:
    print("\nInvalid sequence, only GACT allowed, try again!.\n")
 
# Print some line breaks
print("\n\n")
 
# Prime the list to track the DNA fragments and the variable for the while loop
dnaFragmentInfo = []
dnaFragment = input("Please give a DNA fragment to check:")
 
while dnaFragment:
 
  # Check if present at all
  dnaFragmentCount = fullDnaSequence.count(dnaFragment)
  if dnaFragmentCount:
    currentDnaSequenceIndex = 0
    for i in range(dnaFragmentCount):        
 
      # Equivalent to 
      #currentDnaSequenceIndex = currentDnaSequenceIndex + fullDna...
      currentDnaSequenceIndex += fullDnaSequence[currentDnaSequenceIndex:].index(dnaFragment)
 
      print("\n  Fragment {} present at position {}.\n".format(dnaFragment,currentDnaSequenceIndex + 1))
      dnaFragmentInfo.append((currentDnaSequenceIndex + 1,dnaFragment))
      currentDnaSequenceIndex += 1
  else:
    print("\n  Fragment {} not present!\n".format(dnaFragment))
 
  dnaFragment = input("Please give a DNA fragment to check:")
 
# Print some line breaks
print("\n\n")
 
# Print out the fragment information again, first sort it
dnaFragmentInfo.sort()
for (dnaFragmentPosition,dnaFragment) in dnaFragmentInfo:
 
  print("Found {} at position {}".format(dnaFragment,dnaFragmentPosition))

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