Syntax

Comments

>>> # This is a comment
>>> # print("Hello World!")
... 
>>>

Keywords and Identifiers

False      class      finally    is         return
None       continue   for        lambda     try
True       def        from       nonlocal   while
and        del        global     not        with
as         elif       if         or         yield
assert     else       import     pass
break      except     in         raise

Variables and Datatypes

>>> a = 12
>>> type(a)
<class 'int'>

>>> a = 1.0
>>> type(a)
<class 'float'>

>>> a = "Hello World"
>>> type(a)
<class 'str'>

Strings

>>> 'World'
'World'
>>> "World"
'World'
>>> 'World\'s Best'
"World's Best"
>>> "World's Best"
"World's Best"

Read User Input

>>> number = int(input("Enter a number: "))
Enter a number: 5
>>> print(number)
5

name = str(input("Enter your name: "))
Enter your name: root
>>> print(name)

Multiple Assignments

>>> a, b = 4, 5
>>> a
4
>>> b
5

>>> a, b = b, a
>>> a
5
>>> b
4

Operators

Mathematical
+, -, /, %, *
Logical
and, or
Relational
<, <=, >, >=, ==, !=

Expressions

a = 9
b = 12
c = 3
x = a - b / 3 + c * 2 - 1
y = a - b / (3 + c) * (2 - 1)
z = a - (b / (3 + c) * 2) - 1
print("X = ", x)
print("Y = ", y)
print("Z = ", z)

Type Conversion

float(string) -> float value
int(string) -> integer value
str(integer) -> string representation
str(float) -> string representation

>>> a = 8.126768
>>> str(a)
'8.126768'

Print and string formatting

>>> name = 'Yongyuan'
>>> country = 'China'
>>> print("%s is from %s" % (name, country))
Yongyuan is from China
>>> print("{0} is from {1}".format(name, country))
Yongyuan is from China
>>> print("{} is from {}".format(name, country))
Yongyuan is from China
>>> print("{} is from {}".format(name))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: tuple index out of range

Conditions and Control Flow

if expression:
    do this
elif expression:
    do this
else: 
    do this

Do's and dont's

if x == True:
    do not this  

if x == False:
    do not this

if x:
    do this

if not x:
    do this

Looping

While Loop

while condition:
    statement1
    statement2

>>> # Print 0-10
>>> n = 0 
>>> while n < 11:
...     print(n)
...     n += 1

For Loop

for iterating_var in sequence:
    statement
>>> for i in range(0, 11):  # Print 0-10
...     print(i)

>>> sum = 0
>>> n = 10
>>> for i in range(1, n):
...     sum += i
...
>>> print(sum)
45

Break

>>> word = "Python2 Programming"
>>> for letter in word:
...     if letter == "2":
...         break
...     print(letter)
...
P
y
t
h
o
n

Continue

>>> word = "Python3 Programming"
>>> for letter in word:
...     if letter == "3":
...         continue
...     print(letter)
...
P
y
t
h
o
n

P
r
.

Data structures

List
Tuple
Dictionary
Set
String

Lists

Supports multiple datatypes

>>> list = [1, 2, "hello", 1.0]
>>> list
[1, 2, 'hello', 1.0]

List Operations

>>> a = [23, 45, 1, -3434, 43624356, 234]
>>> a.append(45)
>>> a
[23, 45, 1, -3434, 43624356, 234, 45]

>>> a.insert(0, 111) # Inserts 111 at 0th Position
>>> a
[111, 1, 23, 45, 1, -3434, 43624356, 234, 45]
>>> a.count(45)
2
>>> a.remove(234)
>>> a
[111, 1, 23, 45, 1, -3434, 43624356, 45]

>>> b = [45, 56, 90]
>>> a.append(b)
>>> a [45, 43624356, -3434, 1, 45, 23, 1, 111, [45, 56, 90]]
>>> a[-1]
>>> [45, 56, 90]
>>> a.extend(b) #To add the values of b not the b itself
>>> a
[45, 43624356, -3434, 1, 45, 23, 1, 111, [45, 56, 90], 45, 56, 90]
>>> a[-1]
90
>>> a.remove(b)
>>> a
[45, 43624356, -3434, 1, 45, 23, 1, 111, 45, 56, 90]
>>> a.sort()
>>> a
[-3434, 1, 1, 23, 45, 45, 45, 56, 90, 111, 43624356]

Lists Operations (Stack and Queue)

>>> a = [1, 2, 3, 4, 5, 6]
>>> a
[1, 2, 3, 4, 5, 6]
>>> a.pop() # Pop Operation
6
>>> a.pop()
5
>>> a.pop()
4
>>> a
[1, 2, 3]
>>> a.append(34) # Push Operation
>>> a
[1, 2, 3, 34]
>>> a.append(1)
>>> a
[1, 2, 3, 34, 1]

Lists Comprehensions

>>> a = [1, 2, 3]
>>> [x ** 2 for x in a]
[1, 4, 9]

>>> z = [x + 1 for x in [x ** 2 for x in a]]
>>> z
[2, 5, 10]

Tuple

>>> a = 'Fedora', 'Debian', 10, 12
>>> a
('Fedora', 'Debian', 10, 12)
>>> a[1]
'Debian'
>>> for x in a:
...     print(x, end=' ')
...
Fedora Debian 10 12
>>> type(a)
<class 'tuple'>
>>> len(a)
4

Immutable (Cannot modify any value)

>>> a = (1, 2, 3, 4)
>>> del a[0]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'tuple' object doesn't support item deletion

Tuple Packing & Unpacking

>>> a = (1, 2, 3) # Packing
>>> (first, second, third) = a # Unpacking
>>> first
1
>>> second
2
>>> third
3
>>> (first, second, third) = (1, 2, 3) # Another way

Dictionary

>>> data = {'quentin':'Fedora', 'diwen':'Debian', 'steve':'Mac'}
>>> data
{'quentin': 'Fedora', 'steve': 'Mac', 'diwen': 'Debian'}
>>> data['steve']
'Mac'
>>> data['gerard'] = 'Fedora'
>>> data
{'gerard': 'Fedora', 'quentin': 'Fedora', 'steve': 'Mac', 'diwen': 'Debian'}
>>> del data['steve']
>>> data
{'gerard': 'Fedora', 'quentin': 'Fedora', 'diwen': 'Debian'}

Loop through Dict

>>> for x, y in data.items():
...     print("%s uses %s" % (x, y))
...
gerard uses Fedora
quentin uses Fedora
diwen uses Debian

Sets

>>> a = set('abcthabcjwethddda')
>>> a
{'a', 'c', 'b', 'e', 'd', 'h', 'j', 't', 'w'}
>>> a.add('p')
>>> a
{'a', 'c', 'b', 'e', 'd', 'h', 'j', 'q', 'p', 't', 'w'}

Slicing

List

>>> a = [1, 2, 3, 4, 5, 6, 7]
>>> a[1:4]
[2, 3, 4]
>>> a[:-1]
[1, 2, 3, 4, 5, 6]
>>> a[::-1]
[7, 6, 5, 4, 3, 2, 1] # Reverse

Tuple

>>> a = (1, 2, 3, 4, 5, 6, 7)
>>> a[1:4]
(2, 3, 4)
>>> a[::-1]
(7, 6, 5, 4, 3, 2, 1)

String

>>> a = 'Hello World'
>>> a[0]
'H'
>>> a[5]
' '
>>> a[1:]
'ello World'
>>> a[::-1] # Reverse
'dlroW olleH'

>>> s = "I am Dutch"
>>> s
I am Dutch'
>>> s = "Here is a line \
... split in two lines"
>>> s
'Here is a line split in two lines

>>> s = """ This is a
... multiline string, so you can
... write many lines"""
>>> print(s)
This is a
multiline string, so you can
write many lines

Operations

>>> s = "gerard braad"
>>> s.title()
'Gerard Braad'
>>> z = s.upper()
>>> z
'GERARD BRAAD'
>>> z.lower()
'gerard braad'
>>> s = "123"
>>> s.isdigit()
True
>>> s = "Fedora24"
>>> s.isdigit()
False

Split Method

>>> s = "Let's learn Python3"
>>> s.split(" ")
["Let's", 'learn', 'Python3']

>>> s.split()
["Let's", 'learn', 'Python3']

>>> s = "This is: ME"
>>> s.split(":")
['This is', ' ME']

Join Method

>>> s = "We all love Python."
>>> s.split(".")
['We all love Python', '']

>>> "3".join(s.split("."))
'We all love Python3'

Strip Method

>>> s = "    abc  "
>>> s.strip()
'abc'

>>> # Strip from left hand and right hand size
>>> s = "www.fedoraproject.org"
>>> s.lstrip("www.")
'fedoraproject.org'

>>> s.rstrip(".org")
'www.fedoraproject'

Enumerate

>>> for i, j in enumerate(['a', 'b', 'c']):
...     print(i, j)
...
0 a
1 b
2 c

Functions

def functionname(params):
    statement1
    statement2

>>> def sum(a, b):
...     return a + b

>>> res = sum(2, 3)
>>> res
5

Check Palindrome

>>> def check_palindrome(word):
...     rev_word = word[::-1]
...     if word == rev_word:
...         print("Palindrome")
...     else:
...         print("Not Palindrome")
...
>>> check_palindrome("madam")
Palindrome
>>> check_palindrome("python3")
Not Palindrome

Default Arguments

>>> def test(a , b=-99):
...     if a > b:
...         return True
...     else:
...         return False

>>> test(12, 23)
False
>>> test(12)
True

Keyword Arguments

>>> def func(a, b=5, c=10):
...     print('a is', a, 'and b is', b, 'and c is', c)
...
>>> func(12)
a is 12 and b is 5 and c is 10
>>> func(12, 24)
a is 12 and b is 24 and c is 10
>>> func(12, c = 25)
a is 12 and b is 5 and c is 25
>>> func(a=12)
a is 12 and b is 5 and c is 10

Note: Can not have non-keyword argument after a keyword based argument

File Handling

r - Open with read only mode
w - Open with write mode
a - Open with append mode

Reading File

>>> f = open('sample.txt', 'r')
>>> f.read()
"Hello World.\nLet's learn Python3.\n"
>>> f.close()
>>> f = open('sample.txt', 'r')
>>> f.readline()
'Hello World.\n'
>>> f.readline()
"Let's learn Python3.\n"
>>> f.close()
>>> f = open('sample.txt', 'r')
>>> f.readlines()
['Hello World.\n', "Let's learn Python3.\n"]
>>> f.close()

Loop through Lines

>>> f = open('sample.txt', 'r')
>>> for i in f:
...     if 'Python' in i:
...         print(i)
...    f.close()

Let's learn Python3.

Write and Append

>>> f = open('test.txt', 'w') # Write
>>> f.write("Hello world")
>>> f.close()
>>> f = open('test.txt', 'r')
>>> f.read()
'Hello world'
>>> f.close()
>>> f = open('test.txt', 'a') # Append
>>> f.write(" Python')
>>>f.close()
>>> f = open('test.txt', 'r')
>>> f.read()
"Hello world Python"
>>>f.close()

Using with Statement

>>> with open('sample.txt', 'r') as f:
...     f.read()
...
"Hello World.\nLet's learn Python3.\n"

>>> with open('sample.txt', 'r') as f:
...     for i in f:
...         if 'Python' in i:
...             print(i)
...
Let's learn Python3.

Modules

import module
from module import something
from module import *

math.py

def square(x):
    return x * x

result.py

from math import square
print(square(5))

`name` and `main`

math.py

def square(x):
    return x * x
if __name__ == '__main__':
    print("Result: for square(5) == %d " % square(5))

result.py

import math
print(math.square(5))

Syntax

Comments

Keywords and Identifiers

Variables and Datatypes

Strings

Read User Input

Multiple Assignments

Operators

Expressions

Type Conversion

Print and string formatting

Conditions and Control Flow

Do's and dont's

Looping

While Loop

For Loop

Break

Continue

Data structures

Lists

List Operations

Lists Operations (Stack and Queue)

Lists Comprehensions

Tuple

Immutable (Cannot modify any value)

Tuple Packing & Unpacking

Dictionary

Loop through Dict

Sets

Slicing

List

Tuple

String

Operations

Split Method

Join Method

Strip Method

Enumerate

Functions

Check Palindrome

Default Arguments

Keyword Arguments

File Handling

Reading File

Loop through Lines

Write and Append

Using with Statement

Modules

__name__ and __main__

results matching ""

No results matching ""

`name` and `main`