In [3]:

    

author = 'Kracekumar'
one_liner_about_python = "Python is simple and powerful language"
description = """Python is a general purpose, high level language.
It is dynamically typed and interpretered language.
"""

print(author)
print(one_liner_about_python)
print(description)

complete_msg = """Author: {}
One liner about Python:
- {}
Long Description:
{}""".format(author, one_liner_about_python, description)
print(complete_msg)


    

    




Kracekumar
Python is simple and powerful language
Python is a general purpose, high level language.
It is dynamically typed and interpretered language.

Author: Kracekumar
One liner about Python:
- Python is simple and powerful language
Long Description:
Python is a general purpose, high level language.
It is dynamically typed and interpretered language.

In [6]:

    

print("lower".upper())
print("upper".lower())
print("captialize".capitalize())
print(" extra spaces ".strip()) # Very useful in web development while cleaning user input
print("find a word's position in the sentence".find('word')) # returns starting position
print("how many times the letter `e` is present in the sentence".count('e'))
print("Replace delete with remove".replace('delete', 'remove'))
print("Python is simple and powerful language".startswith('Python'))


    

    




LOWER
upper
Captialize
extra spaces
7
11
Replace remove with remove
True

In [10]:

    

language = 'python'
# Print first character
print(language[0])
# print last character
print(language[-1])
# Find length f the string
print(len(language)) # builtin function
# Print first 3 characters
print(language[0:2]) # Slicing `0` is starting index and `2` is last index
# print last three characters
print(language[-3:])
# Add a dot after python

language = language + "." # Here new variable is created
print(language)


    

    




p
n
6
py
hon
python.

In [12]:

    

print(23 == 32)
print(23 != 32)
print(True == False)
print(True != False)


    

    




False
True
False
True

In [15]:

    

print(True and False)
print(23 and 12) # Watch for output
print(True or False)
print(23 or 12) # Watch for output
print("python" or "javascript")
print("python" and "javascript")
print(not 23)


    

    




False
12
True
23
python
javascript
False

In [35]:

    

collection = ['Python', 23, 45.9, True] # Collection of different elements.
"""Representaion of list
       ---------------------------
       |'python'| 23 | 45.9 | True|
       ---------------------------
        0        1      2      3

"""
print(collection)
# Access the first element
print(collection[0])
# Access the last element
print(collection[-1])
# Replace the first element
collection[0] = 'Go'
print(collection[0])
# Add an element at the last position
collection.append("last")
print(collection[-1])
# Insert an element at position 2
print(collection)
collection.insert(2, 12)
print(collection)
# Delete the last element
del collection[-1]
print(collection)
# Length of the list
print(len(collection))


    

    




['Python', 23, 45.9, True]
Python
True
Go
last
['Go', 23, 45.9, True, 'last']
['Go', 23, 12, 45.9, True, 'last']
['Go', 23, 12, 45.9, True]
5

In [65]:

    

nested_collection = [['apple', 'orange'], ['Python', 'Go']]
print(nested_collection) # Access first element in first list
print(nested_collection[0][0])


    

    




[['apple', 'orange'], ['Python', 'Go']]
apple

In [23]:

    

collection = ['Python', 23, 45.9, True]
print(collection.count(23))
print(collection.index(23)) # If not found Exception will be raised.
print('23' in collection) # Check if an element is present in list
print('p' in 'python') # `in` works on strings, list etc..


    

    




1
1
False
True

In [29]:

    

for i in ['Python', 23, 45.9, True]: # During every iteration i value is replaced, `python` -> `23` -> `45.9` -> `True`
    print(i)


    

    




Python
23
45.9
True

In [25]:

    

for ch in "Python":
    print(ch)


    

    




P
y
t
h
o
n

In [26]:

    

for number in range(0, 10): # Produces list of numbers starting from 0 til 9, 10 is excluded.
    if number % 2 == 0:
        print("Even")
    else:
        print("Odd")


    

    




Even
Odd
Even
Odd
Even
Odd
Even
Odd
Even
Odd

In [30]:

    

def square(x): # No need to specify type of the argument.
    return x * x

def cube(x):
    return square(x) * x

def msg(): # Function with no arguments and doesn't return any value
    print("End")
    
    
print(square(2))
print(square(23))
msg()


    

    




4
529
End

In [32]:

    

def square(x=2): # if x didn't receive any value, 2 is taken.
    return x * x

print(square(23))
print(square(2))


    

    




529
4

In [66]:

    

def fxy(f, x, y): # f(x, y) = f(x) . f(y)
    return f(x) * f(y)

def square(x):
    return x * x

print(fxy(square, 2, 3))


    

    




36

In [44]:

    

print(sum([1, 2, 3, 4])) # 10
print(max([1, 2, 3, 4])) # 4
print(min([1, 2, 3, 4])) # 1
print(sorted([1, 2, 3, 4])) # Ascending order
print(sorted([1, 2, 3, 4], reverse=True)) # Descending order
print(float(23)) # Typecast into float
print(list("23")) # String -> list
print(str(23))
print(int('23'))
# Find data type
print(type(23))
print(type([2]))
print(type('23'))


    

    




10
4
1
[1, 2, 3, 4]
[4, 3, 2, 1]
23.0
['2', '3']
23
23
<type 'int'>
<type 'list'>
<type 'str'>

In [61]:

    

class Person:
    def __init__(self, first_name, last_name='', age=18): # self is always first argument in all instance method
        # __init__ is initializer
        self.first_name = first_name
        # Instance attribute like instance method self. notation is used inside class to assign value
        self.last_name = last_name
        self.__age = age # Private like attribute
        
    def full_name(self):
        # Instance method
        return self.first_name + ' ' + self.last_name
    
    def get_age(self):
        # Since __age is private like variable we need to have getters and setters. Getter
        return self.__age
    
    def set_age(self, age):
        # Setter
        self.__age = age
    
    def is_major(self):
        return self.__age >= 18
    

guido = Person("Guido", "van rossum", 58) # __init__ of Person is called
krace = Person("Kracekumar", "Ramaraju", 24)
# Access instance first_name, last_name
print(guido.first_name)
print(guido.last_name)
print(krace.first_name)
print(krace.last_name)
# Access instance methods
print(guido.full_name()) # self is passed implicitly in the background.
print(krace.is_major())

# Modif the age, first_name
krace.set_age(12)
krace.first_name = 'kracekumar'
print(krace.get_age(), krace.first_name)
print(krace.is_major())


    

    




Guido
van rossum
Kracekumar
Ramaraju
Guido van rossum
True
(12, 'kracekumar')
False

In [54]:

    

months = {'jan': 31, 'feb': 28, 'mar': 31, 'apr': 30} # Colon is used to separate key and value

# `jan` is key and `31` is value
""" Visual representation of Dictionary
-----------
|Key|Value|
-----------
|jan|31   |
-----------
|feb|28   |
-----------
|mar|31   |
-----------
|apr|30   |
-----------
"""
print(months) # Dictionary don't maintain the order of insertion. 
print(months['jan']) # Values in dictionary are accessed using key, in list index is used.
print(months.get('jan')) # .get returns None if the key is missing
print('dec' in months) # `in` is used to check presence of key in dictionary.
print(len(months)) # len function is used to find total key, value pair in dictionary.
for key, value in months.items(): # .items() returns two values during every iteration. First is key, second is value
    print(key, '->', value)
months['feb'] = 29 # Leap year! if key is already present value will be replaced else key, value pair will be added.
print(months)
months['dec'] = 31
print(months)


    

    




{'jan': 31, 'apr': 30, 'mar': 31, 'feb': 28}
31
31
False
4
('jan', '->', 31)
('apr', '->', 30)
('mar', '->', 31)
('feb', '->', 28)
{'jan': 31, 'apr': 30, 'mar': 31, 'feb': 29}
{'jan': 31, 'apr': 30, 'dec': 31, 'mar': 31, 'feb': 29}

In [56]:

    

l = [1, 2, 3]
print(l[5]) # This raises IndexError since list only contains 3 elements.


    

    




---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-56-5e770730b19a> in <module>()
      1 l = [1, 2, 3]
----> 2 print(l[5]) # This raises IndexError since list only contains 3 elements.

IndexError: list index out of range

In [57]:

    

d = {'a': 1}
print(d['b']) # Raises KeyError


    

    




---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-57-945bd7e85bd3> in <module>()
      1 d = {'a': 1}
----> 2 print(d['b']) # Raises KeyError

KeyError: 'b'

In [64]:

    

try:
    l = [1, 2, 3]
    print(l[5])
except IndexError as e:
    print(e)


    

    




list index out of range

In [59]:

    

try:
    d = {'a': 1}
    print(d['b'])
except KeyError as e:
    print(e)


    

    




'b'

In [62]:

    

#### 10.4 Catch all

try:
    l = [1, 3, 3]
    d = {'a': 1}
    print(l[5], d['a'])
except (IndexError, KeyError) as e:
    print(e)
finally:
    print("end")


    

    




list index out of range
end

In [ ]: