Week 5 - Additional Practice Problems

Liaw Bei Le · April 19, 2021

Python   Practices   Reflections

Here are some more challenging practice problems that I did, using what I learnt earlier:

Additional Practices

  • Create & use 2 functions to
    a. find all the prime numbers < a given number, put them in a list& then
    b. return the square of all those prime numbers, in a list     
    '''First get a number from user'''
number_input=int(input("Number: "))
'''Then check if a number is prime'''
def prime_check(inputted_no):
  flag=0
  for number in range(2,inputted_no):
      if inputted_no%number==0:
          flag=1
          break
  return flag
'''Then check if those prime numbers are < the number input by user'''
'''Then square them if yes'''
def squaredprimelist(input_number):
  the_list=[]
  for number in range(2,input_number):
      flag=prime_check(number)
      if flag==0:
          the_list.append(number**2)
  print(the_list)
squaredprimelist(number_input)
  • Iterate thru the numbers before the input number, and return a list of all prime numbers.
    E.g. input = 10 ; output = [2, 3, 5, 7]     
    '''First get a number from user'''
number_input=int(input("Number: "))
'''Then check if a number is prime'''
def prime_check(inputted_no):
  flag=0
  for number in range(2,inputted_no):
      if inputted_no%number==0:
          flag=1
          break
  return flag
'''Then check if those prime numbers are < the number input by user'''
'''Then append them to list if yes'''
def primelist(input_number):
  the_list=[]
  for number in range(2,input_number):
      flag=prime_check(number)
      if flag==0:
          the_list.append(number)
  print(the_list)
primelist(number_input)
  • Print all the number factors of all numbers less than the input number
    E.g. input = 5 ; output = [ [1], [1, 2], [1, 3], [1, 2, 4] ]     
    '''First get a number from user'''
number_input=int(input("Number: "))
'''Find factors of numbers''' 
'''don't forget to return the value at end of custom function'''
def factors_list(inserted_number):
  list_of_factors=[]
  for number in range(1,inserted_number+1):
      if inserted_number%number==0:
          list_of_factors.append(number)
  return list_of_factors
'''if the numbers < input number, then append their list of factors to list'''
def longer_list(inputtedno):
  the_factors_list=[]
  for number in range(1,inputtedno):
      shorter_list=factors_list(number)
      the_factors_list.append(shorter_list)
  print(the_factors_list)
longer_list(number_input)
  • Find length of list without using len( ) function 
    a_list=[1,4,6,8]
def length_list(the_list):
  count=0
  for item in the_list:
      count+=1
  return count
listlength=length_list(a_list)
print(listlength)
  • Compare keys of a dictionary to item in another list, if exist in both, print the key’s value
    for item in another list, if (item ==) key in dictionary, print the key’s value 
    '''create a dictionary of countries & capitals'''
d={}
d['India']='New Delhi'
d['Japan']='Tokyo'
for key in d.keys():
  print(key)
'''compare to another list of countries, if country is in dictionary, print its capital.'''
list_of_countries=['India', 'Singapore', 'Japan']
for country in list_of_countries:
  if country in d:
      print(f"Capital is: {d[country]}")
  else:
      d[country]=''
print(d)

Thoughts

For more complex problems like these, I find it really helps when I write down the thought process of how to solve the problem in comments/ doc strings first, so that I can have an orderly step-by-step guide to know what code I need to write to generate the output. I definitely encountered some problems and had to debug along the way. However, it is also really satisfying when the code finally works well!

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