Variable and data types (int, long, string, float, bool) and structures (list, tuple, dict, set):
v1 = 1 # int or long (bigint) data typehelp(v1) # list of methods and documentations
v1 = (1,'test') # tuple data type
tuple([1,2,'test']) == (1,2,'test') # convert to tuple
list((1,2,'test')) == [1,2,'test'] # convert to list
Operators (arithmetic, comparison, logical, assignment, bitwise, identity/is, membership/in):
v1 = '%s %d %.2f' % ('yay',1,1.2345)
v1 = 1 # int or long (bigint) data type
v1 = 'str' # string data type
dir(v1) # list of methods as array of string
dir(v1) # list of methods as array of string
v1 = 1.2 # float
print(v1.__doc__) # get documentation of current type or method
type(v1) == float
v1 = [1,2,'test'] # list data type
type(v1) == float
v1 = [1,2,'test'] # list data type
v1[-1] == 'test' # True (bool data type)
v1[::2] == [1,'test'] # step each 2
v1[:2] == [1,2] # from beginning until before index 2
v1[1:] == [2,'test'] # from index 1 until the end
range(3) == [0,1,2] # generate from range
range(1,7,2) == [1,3,5] # jump every 2
del v1[1] # delete at pos 1
any([True,1,2,3]) == True
any(['',0,False]) == False
sum([1,2,3]) == 6
v1 = [1,2,3]
v1.append(4) # changes v1 to [1,2,3,4]
v2 = v1[:] # deep copy
v1.pop() # 4
v1.remove(3) # remove first occurence
v1.insert(1,99) # changes v1 to [1,99,2]
v1.index(99) # first 99 found at position 1
v1 + v2 # [1,99,2,1,2,3,4]
v1.extend(v2) # updates v1 to ^
len(v1) # 7
i = iter(v1)
next(i) # 1
v1 = [3,2,1]
v1.sort() # v1 now [1,2,3]
v1 = (1,'test') # tuple data type
tuple([1,2,'test']) == (1,2,'test') # convert to tuple
list((1,2,'test')) == [1,2,'test'] # convert to list
v1[0] == 1 # can be indexed, but readonly
v1 += (2,) # (1,'test',2)
v1 = {'a':1, 2:3} # dict data type
list(v1) == v1.keys()
v1.values() == [1,3]
v1[4] = 5
3 in v1 # False, because no key 3 in v1
v1.get(99) == None
del v1['a']
v1 = set()
v1 = {1,2,2,1,1,3} # {1,2,3}
v1.add(3) # no effect
v1 & {1,2} # intersection
v1 | {3,4} # union
v1 - {1,2} # difference
v1 ^ {1,4} # symetric difference
v1 >= {1,2} # True if right all included in v1
v1.copy() # deep copy
Operators (arithmetic, comparison, logical, assignment, bitwise, identity/is, membership/in):
v1 / 2 # float division
v1 // 2 # integer division
v1 ** 3 # exponentiation
not (v1 > 3) # bool
v1 != 2 and v1 < 5 # bool
v1 != 2 or v1 < 5 # bool
v1 is 3 # only true when referring to same object
3 is 3 # variable with const always false
'test' + '123' # concat
Formatting and conversion:
v1 = '%s %d %.2f' % ('yay',1,1.2345)
v1 == 'yay 1 1.23'
v1 = '%(name)s age is %(age).2f' % {'name':'kis', 'age':34.5}
v1 == 'kis age is 34.50'
v1 = """
multi line {}
""".format('string')
v1 == '\nmulti line string\n'
'%4s' % 'a' == ' a' # 3 space before a, no need for tuple if one
int('2') == 2
float('2.34') == 2.34
str(123.456) == '123.456'
bool(0) # False, also False for '', [], {}, ()
print('yay',end='') # without newline
Control structure (if, for, while):
if 's' in v1:
print('inside')
elif '\n' in v1:
print('have newline')
else:
print('not having s or newline')
for v in v1: # only key if dict, can be iter
print(v) # can use continue or break
else:
print('only called when no break')
while True:
break
# list comprehension
[x * x for x in [1,2,3]] == [1,4,9]
[x * y for x in [1,2,3] for y in [10,20]] == [10,20,30,40,50,60]
# dict comprehension
{x:1 for x in 'abcdef' if x not in 'acf'} == {'b':1,'d':1,'e':1}
Function and lambda:
d = 0
def f1(a,b=2,c='c'):
def f1(a,b=2,c='c'):
global d # if need to modify global variable
d += 1
d += 1
print(a,b,c,d) # print as tuple
f1([],3) # ([],3,'c',1)
f1 = lambda(y): y + 'test'
print(f1('a')) # atest
filter(lambda(x): x%2 == 0, [1,2,3,4,5]) == [2,4]
def f2(*a):
print(a)
f2(1,2,'a') # (1,2,'a')
def f3(**a):
print(a)
f3(x=1,y=2) # {'x':1,'y':2}
v1 = ['a','foo','ca']
v1.sort(key=lambda(x): len(x)) # sort by length
def f4(x):
return -len(x)
v1.sort(key=f4) # without lambda
Class and object:
class Human(object):
static_var = 10
def __init__(self):
self.name = 'kis'
def set_age(self,a):
self.age = a
def get_both(self):
return (self.name,self.age)
def static_method():
return 'whoa'
h = Human()
h.set_age(34)
print(h.get_both())
h.address = 'dzf 1/23' # create new member
del h.address
Human.static_var = 3 # all object points to this new value
h.static_var = 4 # only this object points to this new value
h2 = Human()
h2.static_var == 3 # last time changed from 10 to 3
Importing libraries:
import random
from time import clock
random.seed(clock())
random.seed(clock())
v1 = random.randint(1,10) # inclusive 1 to 10
print(v1)
import math
math.sqrt(9) # 3.0
from math import ceil, floor
ceil(3.4) # 4.0
floor(3.9) # 3.0
import math as m
m.sqrt(4) # 2.0
from heapq import heappush, heappop, heapify
from heapq import heappush, heappop, heapify
v1 = []
heappush(v1,4)
heappush(v1,6)
heappush(v1,5)
heappop(v1) # 4
heappop(v1) # 5
heappop(v1) # 6
v1 = [(4,'a'),(2,'b'),(1,'c'),(3,'d')]
heapify(v1) # heappop() 4 times will return sorted order
from bisect import bisect_left # C++'s lower_bound
from collections import deque
v1 = deque(v1)
v1.appendleft((1,'c'))
bisect_left(v1,(2,'b')) == 1 # returns nearest if not exists
class KV(object):
def __init__(self, l, key):
self.l = l
self.key = key
def __len__(self): # overrides len()
return len(self.l)
def __getitem__(self, index): # overrides []
return self.key(self.l[idx])
def get(self, idx):
return l[idx]
v1 = KV(v1,lambda(x): x[0])
bisect_left(v1,3)
v1 = KV(v1,lambda(x): x[0])
bisect_left(v1,3)
I think that's for now, I exclude try-except-else-finally (or catch all exception) and making a module in this tutorial.
