Week 4 - Using assignment operators, custom functions within functions, return values

Liaw Bei Le · April 16, 2021

Learning   Python   Practices   Reflections
  1. Assignment operators: count=count+1 can be written as count+=1 and so on. Same for *= and -= etc.
  2. Using custom functions within custom functions
  3. Returning more than 1 value - returns the values as items in a tuple.
    Need to create multiple variables (not just 1) for the returned values.
    Can create more than 1 variable for items in list, tuple, strings etc.

& dry run codes when there are bugs (to figure out what went wrong).

What I learnt:

1. Using += , *= , -= etc. to increment and decrement

2. Using custom functions within custom functions

  • Find length of list & multiple and sum of items in list without using len( ) or sum( ) inbuilt functions.
    Use f strings. 
    a_list=[2,5,7,1]
def length_of_list(list1):
  count=0
  for number in list1:
      count+=1
  return count
def multiples(list1):
  times=1
  for number in list1:
      times*=number
  return times
def sum_all(list1):
  summed=0
  for number in list1:
      summed+=number
  return summed
length=length_of_list(a_list)
multiple=multiples(a_list)
summed=sum_all(a_list)
print(f"The length, sum and product are {length}, {summed} and {multiple}.")

    - Continued: -
    For another list of numbers, use the above 3 functions created previously into one custom function and get the length, sum and product of the list.

    diff_list=[1, 2, 3, 4]
def list_info(onelist):
# don't need to put: "for numbers in onelist:"
  added=sum_all(onelist)
  multiplied=multiples(onelist)
  length=length_of_list(onelist)
  return added, multiplied, length
list_information=list_info(diff_list)
print(f"The sum, multiple and length of list is {list_information}.")
  • Find the length of a string without using len( ) function.
    Use f strings. 
    string_1="This is a cat"
def find_length(a_string):
  count=0
  for character in a_string:
      count+=1
  return count
string_length=find_length(string_1)
print(f"Length of string is {string_length}.")

    - Continued: -
    For another string, use the above function created previously into one custom function and get the length of the longest word in the string.
    Use max( ) inbuilt function.

    '''split the sentence into many strings of separate words'''
'''find length of each word and append the length to a list'''
'''use max( ) on the list to find max word length'''
string_2="This is a dog"
def get_longest_wordlength(onestring):
  newlist=onestring.split(' ')
  listoflengths=[]
  for word in newlist:
      wordlength=find_length(word)
      listoflengths.append(wordlength)
  return max(listoflengths)
get_longest_wordlength(string_2)

3. Returning more than 1 value - returns the values as items in a tuple

We can create more than 1 variable for items in list, tuple, strings etc.

  • Find the length of longest word, length of the whole string & frequency of each character in the string in a dictionary.
    All above using 1 custom function 
    mystring="the quick brown fox jumped over the lazy dog in singapore"
# practise this! ***
def mydictionary(onestring):
  d={}
  for character in onestring:
      if character in d:
          d[character]=d[character]+1
      else:
          d[character]=1
  return d
def string_info(thestring):
  '''using custom fxn in above prev example'''
  length_of_word=get_longest_wordlength(thestring)
  '''using custom fxn in above prev example'''
  string_length=find_length(thestring)
  '''using custom fxn in code above here'''
  thedictionary=mydictionary(thestring)
  '''return 3 values at once'''
  return length_of_word, string_length, thedictionary
'''create 3 variables to store the 3 returned values from the custom fxn'''
length_of_word, string_length, thedictionary=string_info(mystring)
print(f"The length of word is {length_of_word}, string length is {string_length}, and frequency of character is {thedictionary}.")

When you return more than 1 value, it gets gets returned as a tuple:

  • Practice example 1: 
    countries=['India', 'Singapore']
country1, country2=countries
print(country1, country2)

    Output:

    India 
Singapore
  • Practice example 2: 
    letter1, letter2='12'
print(letter1, letter2)

    Output:

    1 
2

Thoughts

Custom functions are a bit tricky for me at the moment, especially when we have to insert them into other custom functions for specific tasks/ outputs. The difficult part is getting familiar with where to insert the custom function & figuring out the arguments needed for the custom functions.

In my next post, I will be doing more practices on custom functions and using them, so that I can familiarise and be more confident when using these custom functions.

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