[Python]: Built-in Functions, Examples

Python provides you with a great variety of built-in functions and modules. We wil display a bit of interesting examples here, using some built-in functions.

def biggest_number(*args):
   return max(*args)

As you noticed, we can pass multiple inputs to our function using *args syntax.

# output: 6
print max(4,2,6)

# output: 3
print min(3,6,7)

# output: 98
print abs(-98)

Determining the type of variabel and using it:

# output: displays the types of variables: int, str, float
x_int = 52
x_string = "hello"
x_float = 2.436

print type(x_int) # output: <type 'int'>
print type(x_string) # output: <type 'str'>
print type(x_float) # output: <type 'float'>
# verify the input and increment it if numeric
def increment(number):
    if type(number) == int or type(number) == float:
        return number + 1
    else:
        return False

def increment_input(input):
    result = increment(input)
    if result:
        print "The result is : %s" % result
    else:
        print "Sorry, the input you provided is not a number"

# output: Sorry, the input you provided is not a number
input1 = raw_input("Enter a string: ")
increment_input(input1)

# output: the number provided + 1
input2 = raw_input("Enter a number: ")
input2 = int(input2)
increment_input(input2)

Creating average function

# calculating average with the provided list of numbers
# using pre-built function sum
def average(numbers):
    total = float(sum(numbers))
    total = total / len(numbers)
    return total

print average([2,4,9])

Generating random numbers

from random import randint

random_number = randint(0, 12)

# output: a random number between 0 and 12 
print rand_number

Sum of digits in a number

def digit_sum(n):
    total = 0
    while n != 0:
        number = n % 10
        n = int(n / 10)
        total = total + number
    return total

# output: 10 = 1+2+3+4
print digit_sum(1234)

Factorial function

def factorial(x):
    total = 1
    for number in range(1, x + 1):
        total = total * number
    return total

# output: 24 = 4! = 4 * 3 * 2 * 1 
print factorial(4)

Is Prime number function

def is_prime(x):
    x = abs(x)
    for number in range(0, x):
        # skipping the numbers 0 and 1
        if abs(number) == 0 or abs(number) == 1:
            continue
        # if number can be divided by any other number then it's not a prime number
        if x % number == 0:
            return False
    return True


# output: True
print is_prime(13)

# output: False
print is_prime(12)

# output: True
print is_prime(-11)

String reverse function

def reverse(word):
    reversed_word = ""
    for character in word:
        reversed_word = character + reversed_word
    return reversed_word

# output: emesrever
print reverse('reverseme')

Anti-vowel function

This function will remove the vowel in a string and return a function without vowels.

def anti_vowel(word):
    word_without_vowels = ""
    for character in word:
        if character.lower() in ['a', 'e', 'i', 'o', 'u']:
            continue
        word_without_vowels = word_without_vowels + character
    return word_without_vowels

# output: "Hr y g, dr!"
print anti_vowel("Here you go, dear!")

Counting number of item occurences in the list

def count(sequence, item):
    total = 0
    for search_item in sequence:
        if item == search_item:
            total = total + 1
    return total

# output: 3 (number 2 occurs 3 times in the list)
print count([1,2,3,2,3,2], 2)

Removing odd numbers from the list

def purify(list):
    new_list = []
    for item in list:
        if item % 2 == 0:
            new_list.append(item)
    return new_list


# output: [2] - odd numbers will be removed
print purify([1,2,3])

Multiplying numbers in the list

def product(numbers):
    total = 1
    for number in numbers:
        total = total * number
    return total

# output: 6 = 1*2*3
print product([1,2,3])

Removing duplicates from the list

def remove_duplicates(list):
    clean_list = []
    for item in list:
        if item in clean_list:
            continue
        clean_list.append(item)
    return clean_list

# output: [1,3,4]
print remove_duplicates([1,3,3,4])

Calculating median in the list of numbers

# even number of elements in the list
# taking an average of the middle elements
# otherwise, taking the middle element
def median(numbers):
    numbers = sorted(numbers)
    if len(numbers) == 0:
        return 0

    if len(numbers) % 2 == 0:
        middle = len(numbers) / 2 - 1;
        return float(numbers[middle] + numbers[middle + 1]) / 2
    else:
        middle = (len(numbers) - 1) / 2;
        return numbers[middle]

# output: 0 - median of empty list
print median([])

# output: 5.5
print median([1,2,5,6,7,8])

# output: 3
print median([1,2,3,4,5])

Grades Example: calculating average, variance and standard deviation:

grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]

def print_grades(grades):
    for grade in grades:
        print grade

def grades_sum(grades):
    total = 0
    for grade in grades:
        total = total + grade
    return total

def grades_average(grades):
    return grades_sum(grades) / float(len(grades))

def grades_variance(grades):
    average = grades_average(grades)
    variance = 0
    for grade in grades:
        variance = variance + (average - grade) ** 2
    variance = variance / len(grades)
    return variance

def grades_std_deviation(variance):
    return variance ** 0.5

# output: the grades list, each grade on a single line
print_grades(grades)

# output: 80.4230769231
print 'Average Grade: %s' % grades_average(grades)

# output: 334.071005917
variance = grades_variance(grades)
print 'Variance: %s' % variance

# output: 18.2776094147
print 'Standard Deviation: %s' % grades_std_deviation(variance)

Majd Arbash

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