# The format method
age = '30' or 30
name = 'nawraj'
print('{0} was {1} years old when he wrote this book'.format(name, age))
#decimal (.) precision of 3 for float '0.333'
print('{0:.3}'.format(1/3))
# fill with underscores (_) with the text centered (^) to 11 width '___hello___'
print('{0:_^11}'.format('hello'))
#keyword based, nawraj wrote a Byte of Python
print('{name} wrote {book}'.format(name='nawraj',book='A Byte of Python'))
## multiline in python
s = '''This is a multi-line string.
This is the second line...'''
print(s)
s = 'This is a string. \
This continues the string.'
print(s)
#or
print\
(s)
or
## break statement
while True:
s = input('Enter something: ')
if s == 'quit':
break
print('length of the string is:', len(s))
print('Done')
## continue statement
while True:
s = input('Enter something: ')
if s == 'quit':
break
if len(s) < 3:
print('too small')
continue
print('Input is of insufficient length')
## local variables
x = 50
def func(x):
print('x is', x)
x = 2
print('changed local x to', x)
func(x)
print('x is still', x)
## global statement
x = 50
def func():
global x
print('x is', x)
x = 2
print('changed global x to', x)
func()
print('Value of x is', x)
## default argument
def say(message, times = 1):
print(message * times)
say('hello')
say('World', 5)
##keyword arguments
def func(a, b=5, c=10):
print('a is', a, 'and b is', b, 'and c is', c)
func(3,7)
func(25, c=24)
func(c=50, a=100)
##VarArgs parameters
def total(initial=50, *numbers, **keywords):
count = initial
for number in numbers:
count += number
for key in keywords:
count += keywords[key]
return count
print(total(10, 1, 2, 3, vegetables=50, fruits=100))
## keyword-only parameters
def total(initial=5, *numbers, extra_number):
count = initial
for number in numbers:
count += number
count += extra_number
print(count)
total(10, 1, 2, 3, extra_number=50)
##return statement
def maximum(x,y):
if x > y:
return x
elif x == y:
return 'The number are equal'
else:
return y
print(maximum(3,3))
## DocStrings
def printMax(x,y):
'''print the maximum of two numbers.
The two values must be integers..'''
x = int(x)
y = int(y)
if x > y:
print(x, 'is maximum')
else:
print(y, 'is maximum')
printMax(3,5)
print(printMax.__doc__)
## Modules
import sys
print('The command line arguments are: ')
for i in sys.argv:
print(i)
print('\n\nThe PYTHONPATH is', sys.path, '\n')
## module name
if __name__ == '__main__':
print('This program is being run by itself')
else:
print('I am being imported from other module')
## dir function
import sys
print(dir(sys))
print(dir())
## List
shoplist = ['apple', 'mango', 'carrot', 'banana']
print('i have', len(shoplist), 'items to purchase')
print('These items are:', end= ' ')
for item in shoplist:
print(item, end= ' ')
print('\n I also have to buy rice.')
shoplist.append('rice')
print('My shopping list is now', shoplist)
print('i will sort my list now')
shoplist.sort()
print('sorted shopping list is now', shoplist)
print('The first item i will buy is', shoplist[0])
olditem = shoplist[0]
del shoplist[0]
print('i bought the', olditem)
print('My shopping list is now', shoplist)
## Tuple
zoo = ('python','elephant','penguin')
print('Number of elements in the zoo', len(zoo))
new_zoo = 'monkey', 'camel', 'zoo'
print(type(new_zoo))
print('number of cages in the new zoo : ', len(new_zoo))
print('All animals in the new zoo are ', new_zoo)
print('Animals brought from old zoo are', new_zoo[2])
print('Last animal brought from the old zoo is', new_zoo[2][2])
print('Number of animals in the new zoo is', len(new_zoo)-1+len(new_zoo[2]))
## dictionary
ab = {'nawraj' : 'nawraj.lekhak@hotmail.com',
'Mohan' : 'mohan@hotmail.com',
'Ram' : 'Ram@hotmail.com',
}
print('nawraj addres is: ', ab['nawraj'])
print('There are {0} contacts in the address book'.format(len(ab)))
for name, address in ab.items():
print('Contact {0} at {1}'.format(name, address))
ab['John'] = 'john@hotmail.com'
if 'John' in ab:
print('John address is', ab['John'])
## Sequence
shoplist = ['apple','mango','carrot','banana']
name = 'nawraj'
print('Item 0 is', shoplist[0])
print('Item 1 is', shoplist[1])
print('Item 2 is', shoplist[2])
print('Item 3 is', shoplist[3])
print('Item -1 is', shoplist[-1])
print('Item -2 is', shoplist[-2])
print('Item -3 is', shoplist[-3])
print('Character 0 is', name[0])
print('Item 1 to 3 is', shoplist[1:3])
print('Item 2 to end is', shoplist[2:])
print(shoplist)
print('Item 1 to -1 is', shoplist[1:-1])
print('Item start to end is', shoplist[:])
print('Character 1 to 3 is', name[1:3])
print('Character 2 to end is', name[2:])
print('Character 1 to -1 is', name[1:-1])
print('Character start to end is', name[:])
print(shoplist[::1])
print(shoplist[::2])
print(shoplist[::3])
print(shoplist[::-1])
# set
bri = set(['brazil','russia','india'])
'india' in bri
'usa' in bri
bric = bri.copy()
bric.add('china')
print(bric)
bric.issuperset(bri)
print(bric)
bri.remove('russia')
print(bri)
bri & bric # OR bri.intersection(bric)
print(bri)
print(bric)
## References
print('Simple assignment')
shoplist = ['apple', 'mango', 'carrot','banana']
mylist = shoplist
del shoplist[0]
print('shoplist is:', shoplist)
print('mylits is:', mylist)
==> both will print same list
print('Copy by making a full slice')
mylist = shoplist[:]
del mylist[0]
print('shoplist is ', shoplist)
print('mylist is', mylist)
==> now the two list are different
## Strings
name = 'nawraj'
if name.startswith('naw'):
print('Yes, the string starts with "naw"')
if 'a' in name:
print('Yes, it contains the string "a"')
if name.find('raj') != -1:
print('Yes, it contains the string "raj"')
delimiter = '_*_'
mylist = ['Brazil','Russia', 'India', 'Nepal']
print(delimiter.join(mylist))
## import
import os
import time
source = '/Users/nawlekha/python_training'
target_dir = '/Users/nawlekha/test'
today = target_dir + os.sep + time.strftime('%Y%m%d')
now = time.strftime('%H%M%S')
comment = input('Enter a comment --')
if len(comment) == 0:
target = today + os.sep + now + '.zip'
else:
target = today + os.sep + now + '_' + \
comment.replace(' ', '_') + '.zip'
if not os.path.exists(today):
os.mkdir(today)
print('Successfully created directory', today)
zip_command = 'zip -qr {0} {1}'.format(target, ' '.join(source))
if os.system(zip_command) == 0:
print('successful backup to', target)
else:
print('Backup failed')
## Classes
class Person():
pass
p = Person()
print(p)
## Object Modules
class Person:
def sayHi(self):
print('Hello, how are you?')
p = Person()
p.sayHi()
#or
Person().sayHi()
## The init method
class Person:
def __init__(self, name):
self.name = name
def sayHi(self):
print('Hello, my name is', self.name)
p = Person('nawraj')
p.sayHi()
#or
Person('nawraj').sayHi()
## class and object variables
class Robot:
population = 0
def __init__(self, name):
self.name = name
print('Initializing {0}'.format(self.name))
Robot.population += 1
def __del__(self):
print('{0} is being destroyed!'.format(self.name))
Robot.population -= 1
if Robot.population == 0:
print('{0} was the last one'.format(self.name))
else:
print('There are still {0:d} robots working'.format(Robot.population))
def sayHi(self):
print('Greetings, my masters call me {0}'.format(self.name))
def howMany():
print('We have {0:d} robots'.format(Robot.population))
howMany = staticmethod(howMany)
droid1 = Robot('R2-D2')
droid1.sayHi()
Robot.howMany()
droid2 = Robot('C-3PO')
droid2.sayHi()
Robot.howMany()
print('\nRobots can do some work here.\n')
print('Robots have finished their work. so let destroy them.')
del droid1
del droid2
Robot.howMany()
## Inheritance
class SchoolMember:
def __init__(self,name,age):
self.name = name
self.age = age
print('Initialized schoolmember: {0}'.format(self.name))
def tell(self):
print('name: "{0}", Age: "{1}"'.format(self.name, self.age), end='')
class Teacher(SchoolMember):
def __init__(self, name, age, salary):
SchoolMember.__init__(self, name, age)
self.salary = salary
print('Initialized teacher: {0}'.format(self.name))
def tell(self):
SchoolMember.tell(self)
print('Salary: "{0:d}"'.format(self.salary))
class Student(SchoolMember):
def __init__(self, name, age, marks):
SchoolMember.__init__(self, name, age)
self.marks = marks
print('Initialized student: {0}'.format(self.name))
def tell(self):
SchoolMember.tell(self)
print('Marks: "{0:d}"'.format(self.marks))
t = Teacher('Mr shiva', 40, 30000)
s = Student('nawraj', 25, 80)
print() # print blank line
members = [t, s]
for member in members:
member.tell()
## Input from the user
def reverse(text):
return text[::-1]
def is_palindrome(text):
return text == reverse(text)
something = input('Enter text: ')
if (is_palindrome(something)):
print('Yes, it is palindrome')
else:
print('No, it is not a palindrome')
## Files
one = '''\
hello world
how are you doing
have fun
'''
f = open('one.txt', 'w')
f.write(one)
f.close()
f = open('one.txt') ## r is default mode
while True:
line = f.readline()
if len(line) == 0:
break
print(line, end=' ')
f.close()
## Pickle : use to store any Python object in a file and then get it back later
import pickle
shoplistfile = 'shoplist.data'
shoplist = ['apple', 'mango', 'carrot']
f = open(shoplistfile, 'wb')
pickle.dump(shoplist, f) ## dump the object to the file
f.close()
del shoplist
f = open(shoplistfile, 'rb')
storedlist = pickle.load(f) # load the object from the file
print(storedlist)
## Handling Exceptions
try:
text = input("Enter something-->") ## pres ctrl-d
except EOFError:
print("Why did you do EOF on me? ")
except KeyboardInterrupt:
print('You cancelled the operation')
else:
print('You entered {}'.format(text))
## Raising exception
class ShortInputException(Exception):
def __init__(self, length, atleast):
Exception.__init__(self)
self.length = length
self.atleast = atleast
try:
text = input('Enter something->')
if len(text) < 3:
raise ShortInputException(len(text), 3)
except EOFError:
print('Why did you do an EOF on me')
except ShortInputException as ex:
print('ShortInputException: The input was {0} long, expected at least {1}'.format(ex.length,ex.atleast))
else:
print('No exception raised')
## Try
import time
try:
f = open('one.txt')
while True:
line = f.readline()
if len(line) == 0:
break
print(line, end= ' ')
time.sleep(2)
except KeyboardInterrupt:
print('!! you cancelled reading from the file')
finally:
f.close()
print('CLeaning up. file closed.')
# with statement
with open("one.txt") as f:
for line in f:
print(line, end= " ")
## Logging module
import os, platform, logging
if platform.platform().startswith('Windows'):
logging_file = os.path.join(os.getenv('HOMEDRIVE'),
os.getenv('HOMEPATH'))
else:
logging_file = os.path.join(os.getenv('HOME'), 'test.log')
print('Logging to', logging_file)
## Passing tuple
a, *b = [1,2,3,4]
print(a)
print(b)
# swap
a = 5; b =8
a, b = b, a
print(a, b)
# Single statement block
flag = True
if flag: print("Yes")
## Lambda Forms : used to create new function objects.
points = [{'x' : 2, 'y': 3}, {'x' : 4, 'y' : 1}]
points.sort(key=lambda i : i['y'])
print(points)
# list comprehension
listone = [2, 3, 4]
listtwo = [2*i for i in listone if i > 2]
print(listtwo)
# Receiving tuples and dictionaries in functions
def powersum(power, *args):
total = 0
for i in args:
total += pow(i, power)
return total
powersum(2, 3, 4)
## assert statement
mylist = ['item']
assert len(mylist) >= 1
mylist.pop()
print(mylist)
assert len(mylist) >= 1
## Escape sequence
cmd = "This is the first sentence. \
This is the second sentence"
print(cmd)
age = '30' or 30
name = 'nawraj'
print('{0} was {1} years old when he wrote this book'.format(name, age))
#decimal (.) precision of 3 for float '0.333'
print('{0:.3}'.format(1/3))
# fill with underscores (_) with the text centered (^) to 11 width '___hello___'
print('{0:_^11}'.format('hello'))
#keyword based, nawraj wrote a Byte of Python
print('{name} wrote {book}'.format(name='nawraj',book='A Byte of Python'))
## multiline in python
s = '''This is a multi-line string.
This is the second line...'''
print(s)
s = 'This is a string. \
This continues the string.'
print(s)
#or
print\
(s)
or
if False: '''
...statements...
'''
## break statement
while True:
s = input('Enter something: ')
if s == 'quit':
break
print('length of the string is:', len(s))
print('Done')
## continue statement
while True:
s = input('Enter something: ')
if s == 'quit':
break
if len(s) < 3:
print('too small')
continue
print('Input is of insufficient length')
## local variables
x = 50
def func(x):
print('x is', x)
x = 2
print('changed local x to', x)
func(x)
print('x is still', x)
## global statement
x = 50
def func():
global x
print('x is', x)
x = 2
print('changed global x to', x)
func()
print('Value of x is', x)
## default argument
def say(message, times = 1):
print(message * times)
say('hello')
say('World', 5)
##keyword arguments
def func(a, b=5, c=10):
print('a is', a, 'and b is', b, 'and c is', c)
func(3,7)
func(25, c=24)
func(c=50, a=100)
##VarArgs parameters
def total(initial=50, *numbers, **keywords):
count = initial
for number in numbers:
count += number
for key in keywords:
count += keywords[key]
return count
print(total(10, 1, 2, 3, vegetables=50, fruits=100))
## keyword-only parameters
def total(initial=5, *numbers, extra_number):
count = initial
for number in numbers:
count += number
count += extra_number
print(count)
total(10, 1, 2, 3, extra_number=50)
##return statement
def maximum(x,y):
if x > y:
return x
elif x == y:
return 'The number are equal'
else:
return y
print(maximum(3,3))
## DocStrings
def printMax(x,y):
'''print the maximum of two numbers.
The two values must be integers..'''
x = int(x)
y = int(y)
if x > y:
print(x, 'is maximum')
else:
print(y, 'is maximum')
printMax(3,5)
print(printMax.__doc__)
## Modules
import sys
print('The command line arguments are: ')
for i in sys.argv:
print(i)
print('\n\nThe PYTHONPATH is', sys.path, '\n')
## module name
if __name__ == '__main__':
print('This program is being run by itself')
else:
print('I am being imported from other module')
## dir function
import sys
print(dir(sys))
print(dir())
## List
shoplist = ['apple', 'mango', 'carrot', 'banana']
print('i have', len(shoplist), 'items to purchase')
print('These items are:', end= ' ')
for item in shoplist:
print(item, end= ' ')
print('\n I also have to buy rice.')
shoplist.append('rice')
print('My shopping list is now', shoplist)
print('i will sort my list now')
shoplist.sort()
print('sorted shopping list is now', shoplist)
print('The first item i will buy is', shoplist[0])
olditem = shoplist[0]
del shoplist[0]
print('i bought the', olditem)
print('My shopping list is now', shoplist)
## Tuple
zoo = ('python','elephant','penguin')
print('Number of elements in the zoo', len(zoo))
new_zoo = 'monkey', 'camel', 'zoo'
print(type(new_zoo))
print('number of cages in the new zoo : ', len(new_zoo))
print('All animals in the new zoo are ', new_zoo)
print('Animals brought from old zoo are', new_zoo[2])
print('Last animal brought from the old zoo is', new_zoo[2][2])
print('Number of animals in the new zoo is', len(new_zoo)-1+len(new_zoo[2]))
## dictionary
ab = {'nawraj' : 'nawraj.lekhak@hotmail.com',
'Mohan' : 'mohan@hotmail.com',
'Ram' : 'Ram@hotmail.com',
}
print('nawraj addres is: ', ab['nawraj'])
print('There are {0} contacts in the address book'.format(len(ab)))
for name, address in ab.items():
print('Contact {0} at {1}'.format(name, address))
ab['John'] = 'john@hotmail.com'
if 'John' in ab:
print('John address is', ab['John'])
## Sequence
shoplist = ['apple','mango','carrot','banana']
name = 'nawraj'
print('Item 0 is', shoplist[0])
print('Item 1 is', shoplist[1])
print('Item 2 is', shoplist[2])
print('Item 3 is', shoplist[3])
print('Item -1 is', shoplist[-1])
print('Item -2 is', shoplist[-2])
print('Item -3 is', shoplist[-3])
print('Character 0 is', name[0])
print('Item 1 to 3 is', shoplist[1:3])
print('Item 2 to end is', shoplist[2:])
print(shoplist)
print('Item 1 to -1 is', shoplist[1:-1])
print('Item start to end is', shoplist[:])
print('Character 1 to 3 is', name[1:3])
print('Character 2 to end is', name[2:])
print('Character 1 to -1 is', name[1:-1])
print('Character start to end is', name[:])
print(shoplist[::1])
print(shoplist[::2])
print(shoplist[::3])
print(shoplist[::-1])
# set
bri = set(['brazil','russia','india'])
'india' in bri
'usa' in bri
bric = bri.copy()
bric.add('china')
print(bric)
bric.issuperset(bri)
print(bric)
bri.remove('russia')
print(bri)
bri & bric # OR bri.intersection(bric)
print(bri)
print(bric)
## References
print('Simple assignment')
shoplist = ['apple', 'mango', 'carrot','banana']
mylist = shoplist
del shoplist[0]
print('shoplist is:', shoplist)
print('mylits is:', mylist)
==> both will print same list
print('Copy by making a full slice')
mylist = shoplist[:]
del mylist[0]
print('shoplist is ', shoplist)
print('mylist is', mylist)
==> now the two list are different
## Strings
name = 'nawraj'
if name.startswith('naw'):
print('Yes, the string starts with "naw"')
if 'a' in name:
print('Yes, it contains the string "a"')
if name.find('raj') != -1:
print('Yes, it contains the string "raj"')
delimiter = '_*_'
mylist = ['Brazil','Russia', 'India', 'Nepal']
print(delimiter.join(mylist))
## import
import os
import time
source = '/Users/nawlekha/python_training'
target_dir = '/Users/nawlekha/test'
today = target_dir + os.sep + time.strftime('%Y%m%d')
now = time.strftime('%H%M%S')
comment = input('Enter a comment --')
if len(comment) == 0:
target = today + os.sep + now + '.zip'
else:
target = today + os.sep + now + '_' + \
comment.replace(' ', '_') + '.zip'
if not os.path.exists(today):
os.mkdir(today)
print('Successfully created directory', today)
zip_command = 'zip -qr {0} {1}'.format(target, ' '.join(source))
if os.system(zip_command) == 0:
print('successful backup to', target)
else:
print('Backup failed')
## Classes
class Person():
pass
p = Person()
print(p)
## Object Modules
class Person:
def sayHi(self):
print('Hello, how are you?')
p = Person()
p.sayHi()
#or
Person().sayHi()
## The init method
class Person:
def __init__(self, name):
self.name = name
def sayHi(self):
print('Hello, my name is', self.name)
p = Person('nawraj')
p.sayHi()
#or
Person('nawraj').sayHi()
## class and object variables
class Robot:
population = 0
def __init__(self, name):
self.name = name
print('Initializing {0}'.format(self.name))
Robot.population += 1
def __del__(self):
print('{0} is being destroyed!'.format(self.name))
Robot.population -= 1
if Robot.population == 0:
print('{0} was the last one'.format(self.name))
else:
print('There are still {0:d} robots working'.format(Robot.population))
def sayHi(self):
print('Greetings, my masters call me {0}'.format(self.name))
def howMany():
print('We have {0:d} robots'.format(Robot.population))
howMany = staticmethod(howMany)
droid1 = Robot('R2-D2')
droid1.sayHi()
Robot.howMany()
droid2 = Robot('C-3PO')
droid2.sayHi()
Robot.howMany()
print('\nRobots can do some work here.\n')
print('Robots have finished their work. so let destroy them.')
del droid1
del droid2
Robot.howMany()
## Inheritance
class SchoolMember:
def __init__(self,name,age):
self.name = name
self.age = age
print('Initialized schoolmember: {0}'.format(self.name))
def tell(self):
print('name: "{0}", Age: "{1}"'.format(self.name, self.age), end='')
class Teacher(SchoolMember):
def __init__(self, name, age, salary):
SchoolMember.__init__(self, name, age)
self.salary = salary
print('Initialized teacher: {0}'.format(self.name))
def tell(self):
SchoolMember.tell(self)
print('Salary: "{0:d}"'.format(self.salary))
class Student(SchoolMember):
def __init__(self, name, age, marks):
SchoolMember.__init__(self, name, age)
self.marks = marks
print('Initialized student: {0}'.format(self.name))
def tell(self):
SchoolMember.tell(self)
print('Marks: "{0:d}"'.format(self.marks))
t = Teacher('Mr shiva', 40, 30000)
s = Student('nawraj', 25, 80)
print() # print blank line
members = [t, s]
for member in members:
member.tell()
## Input from the user
def reverse(text):
return text[::-1]
def is_palindrome(text):
return text == reverse(text)
something = input('Enter text: ')
if (is_palindrome(something)):
print('Yes, it is palindrome')
else:
print('No, it is not a palindrome')
## Files
one = '''\
hello world
how are you doing
have fun
'''
f = open('one.txt', 'w')
f.write(one)
f.close()
f = open('one.txt') ## r is default mode
while True:
line = f.readline()
if len(line) == 0:
break
print(line, end=' ')
f.close()
## Pickle : use to store any Python object in a file and then get it back later
import pickle
shoplistfile = 'shoplist.data'
shoplist = ['apple', 'mango', 'carrot']
f = open(shoplistfile, 'wb')
pickle.dump(shoplist, f) ## dump the object to the file
f.close()
del shoplist
f = open(shoplistfile, 'rb')
storedlist = pickle.load(f) # load the object from the file
print(storedlist)
## Handling Exceptions
try:
text = input("Enter something-->") ## pres ctrl-d
except EOFError:
print("Why did you do EOF on me? ")
except KeyboardInterrupt:
print('You cancelled the operation')
else:
print('You entered {}'.format(text))
## Raising exception
class ShortInputException(Exception):
def __init__(self, length, atleast):
Exception.__init__(self)
self.length = length
self.atleast = atleast
try:
text = input('Enter something->')
if len(text) < 3:
raise ShortInputException(len(text), 3)
except EOFError:
print('Why did you do an EOF on me')
except ShortInputException as ex:
print('ShortInputException: The input was {0} long, expected at least {1}'.format(ex.length,ex.atleast))
else:
print('No exception raised')
## Try
import time
try:
f = open('one.txt')
while True:
line = f.readline()
if len(line) == 0:
break
print(line, end= ' ')
time.sleep(2)
except KeyboardInterrupt:
print('!! you cancelled reading from the file')
finally:
f.close()
print('CLeaning up. file closed.')
# with statement
with open("one.txt") as f:
for line in f:
print(line, end= " ")
## Logging module
import os, platform, logging
if platform.platform().startswith('Windows'):
logging_file = os.path.join(os.getenv('HOMEDRIVE'),
os.getenv('HOMEPATH'))
else:
logging_file = os.path.join(os.getenv('HOME'), 'test.log')
print('Logging to', logging_file)
## Passing tuple
a, *b = [1,2,3,4]
print(a)
print(b)
# swap
a = 5; b =8
a, b = b, a
print(a, b)
# Single statement block
flag = True
if flag: print("Yes")
## Lambda Forms : used to create new function objects.
points = [{'x' : 2, 'y': 3}, {'x' : 4, 'y' : 1}]
points.sort(key=lambda i : i['y'])
print(points)
# list comprehension
listone = [2, 3, 4]
listtwo = [2*i for i in listone if i > 2]
print(listtwo)
# Receiving tuples and dictionaries in functions
def powersum(power, *args):
total = 0
for i in args:
total += pow(i, power)
return total
powersum(2, 3, 4)
## assert statement
mylist = ['item']
assert len(mylist) >= 1
mylist.pop()
print(mylist)
assert len(mylist) >= 1
## Escape sequence
cmd = "This is the first sentence. \
This is the second sentence"
print(cmd)
