1. Flow Control
1.1 If
import sys
if sys.version_info.major < 3:
print("Version 2.X")
elif sys.version_info.major > 3:
print("Future")
else:
print("Version 3.X")
Version 3.X
1.2 Loop
1.2.1 For
for i in "Hello":
print(i)
H
e
l
l
o
1.2.2 While
prod = 1
i = 1
while i < 10:
prod = prod * i
i += 1
print(prod)
362880
1.2.3 Break / Continue
for n in range(2, 10):
if n % 2 == 0:
print("Found an even number ", n)
continue
if n > 5:
print("Greater Than 5!")
break
Found an even number 2
Found an even number 4
Found an even number 6
Greater Than 5!
1.2.4 Iterators & Generators **
python = iter("Python")
print(python)
for i in python:
print(i)
P
y
t
h
o
n
def reverse(data):
for index in range(len(data)-1, -1, -1):
yield data[index]
nohtyp = reverse("Python")
print(nohtyp)
for i in nohtyp:
print(i)
n
o
h
t
y
P
1.3 Comprehensions
1.3.1 List
s = [2 * x for x in range(10) if x ** 2 > 3]
print(s)
[4, 6, 8, 10, 12, 14, 16, 18]
pairs = [(x, y) for x in range(2) for y in range(2)]
print(pairs)
[(0, 0), (0, 1), (1, 0), (1, 1)]
1.3.2 Set
s = {2 * x for x in range(10) if x ** 2 > 3}
print(s)
{4, 6, 8, 10, 12, 14, 16, 18}
pairs = {(x, y) for x in range(2) for y in range(2)}
print(pairs)
{(0, 1), (1, 0), (0, 0), (1, 1)}
1.3.3 Dict
ls = {s: len(s) for s in ["Python", "Javascript", "Golang"]}
print(ls)
sl = {v: k for k, v in ls.items()}
print(sl)
{'Golang': 6, 'Javascript': 10, 'Python': 6}
{10: 'Javascript', 6: 'Python'}
2. Functions
2.1 Definition
def f():
"""
return 'Hello World!'
"""
return "Hello World!"
print(f())
print(f.__doc__)
Hello World!
return 'Hello World!'
2.2 Default Arguments
def f(name="World"):
"""
return 'Hello, $name'
"""
return "Hello, {}!".format(name)
print(f())
print(f("Python"))
Hello, World!
Hello, Python!
2.3 Keyword Arguments
def f(v, l="Python"):
"""
return '$v, $l'
"""
return "{}, {}".format(v, l)
print(f("Hello"))
print(f("Bye", "C++"))
Hello, Python
Bye, C++
2.4 Arbitrary Arguments
def f(*args, con=' & '):
print(isinstance(args, tuple))
print("Hello", con.join(args))
f("Python", "C", "C++", con = '/')
True
Hello Python/C/C++
def f(*args, **kargs):
print("args ", args)
print("krags ", kargs)
print("FP: {} & Scripts: {}".format(kargs.get("fp"), '/'.join(args)))
f("Python", "Javascript", ms="C++", fp='Haskell')
args ('Python', 'Javascript')
krags {'ms': 'C++', 'fp': 'Haskell'}
FP: Haskell & Scripts: Python/Javascript
2.5 Lambda
pairs = [(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four')]
pairs.sort(key=lambda pair: pair[1])
print(pairs)
pairs.sort(key=lambda pair: pair[0])
print(pairs)
[(4, 'four'), (1, 'one'), (3, 'three'), (2, 'two')]
[(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four')]
2.6 Decorator
def log(f):
def wrapper():
print("Hey log~")
f()
print("Bye log~")
return wrapper
@log
def fa():
print("This is fa!")
def fb():
print("This is fb!")
fb = log(fb)
fa()
print("*" * 10)
fb()
Hey log~
This is fa!
Bye log~
**********
Hey log~
This is fb!
Bye log~
3. Class (OOP)
3.1 Class
class Animal:
"""
This is an Animal
"""
def fly(self):
print("I can fly!")
a = Animal()
a.fly()
print(a.__doc__)
I can fly!
This is an Animal
3.2 _init_ & self
class Animal:
"""
This is an Animal
"""
def __init__(self, can_fly=False):
print("Calling __init__() when instantiation!")
self.can_fly = can_fly
def fly(self):
if self.can_fly:
print("I can fly!")
else:
print("I can not fly!")
a = Animal()
a.fly()
b = Animal(can_fly = True)
b.fly()
Calling __init__() when instantiation!
I can not fly!
Calling __init__() when instantiation!
I can fly!
3.3 Instance
class Animal:
pass
class Human:
pass
a = Animal()
b = Human()
print(isinstance(a,Animal))
print(isinstance(b,Animal))
True
False
3.4 Inheritance
class Animal:
"""
This is an Animal
"""
def __init__(self, can_fly=False):
self.can_fly = can_fly
def fly(self):
if self.can_fly:
print("I can fly!")
else:
print("I can not fly!")
class Dog(Animal):
"""
This is a Dog
"""
def bark(self):
print("Woof!")
d = Dog()
d.fly()
d.bark()
I can not fly!
Woof!
3.5 Override
class Animal:
"""
This is an Animal
"""
def __init__(self, can_fly=False):
self.can_fly = can_fly
def fly(self):
if self.can_fly:
print("I can fly!")
else:
print("I can not fly!")
class Bird:
"""
This is a Bird
"""
def fly(self):
print("I am flying high!")
bird = Bird()
bird.fly()
I am flying high!