Python : Important code snippets

Important code Snippets

==============Data and Time: ==============
import datetime
print (datetime.datetime.now().day) # Result : 11
==============sorting reverse in list==============
liste=[1,5,9,2,3]
liste.sort(key=None, reverse=False)

Method2

Print(liste[::-1]
==============remove duplicates in list==============
l=[1,5,5,9,"a","b"]
liste=list(set(l))
==============Regex==============

import re

if(re.search(“.*ant.*”,”antelope”)):     #search

   print(True)

print(re.sub(r”expr”,string))              #replace

print(len(re.findall(“expr”,string))      #count

==============locals()==============
def test():
    a = 1
    b = 2
    c= 3
    return locals()
s=test()
print(s) #o/p: (a,1) ,(b,2),(c,3),
print (type(s)) # result : dict
==============Ranged if Condition==============
r=300
if (r in range(200,210,1)):
    print (True)
else:
    print(False)

or

if(200<r<210):
==============Validate type ==============
if isinstance(d,dict):print("hi")
if(type(d)==dict) :print(“True”)
====Higher order  functions (function name as) ====
def a():
    print("hi")
def b(func):
    func()
b(a) # result :hi
====Higher order class (function name as) ====
class deco :   
    def func1(self):
        print ("funct1") 
    def func2(self,var):
        print(var)
              
def some_func(obj):
    obj(deco)
def some_func2(obj,var):
    obj(deco,var) 
  
some_func(deco.func1) #O/p funct1
some_func2(deco.func2,"33") #O/p: 33

==============Keyword Arguments in a Function==============
def a(a=5,b): #wrong - non keyword args follow keyword ie., b should come before a
    print(a,b)
def a(b,a=5): #Correct
    print(a,b)
a(b=3,a=1)    #Result - 31
a(1,2)        #Result - 12
a(a=4,4)     #Error - non Keyword argument should come before keyword argument
=========List and tuple Arbitrary Argument in Function==============
def a(*a):
    for i in a:
        print(i)
a([1,2,3])
a((1,2,3))
Result:
[1,2,3]
(1,2,3)

==============Create sequential lists in 1 line==============
x=list(range(51,60,2))     #[51, 53, 55, 57, 59]

==============Slicing techniques==============

a=list(range(1,5))           #[1,2,3,4]

print(a[::-1])                                    #[4,3,2,1]  -reverse

print(a[::2])                   #[1,3]

print(a[::-2])                                    #[3,1]

print(a[1:-1:1])              #[2,3]

print(a[1:-1:-1])             #[]

print(a[-1:1:-1)]             #[4,3]

==============List into sublist or 1D to 2D==============

a=list(range(1,5))           #[1,2,3,4]

res=[a[i:i+2] for i in range(0,len(a),2)] #[[1,2][3,4]]
method2
m=[[i for i in range(j,j+3)] for j in range(1,7,3)]
#m = [[1, 2, 3], [4, 5, 6]]
===========Transpose a matrix using list comprehensions==============
n=[[m[i][j] for i in range(0,len(m))] for j in range(0,len(m[0]))]

Zip Matrix Transpose

n=list(zip(*m))              #list(zip(m[0],m[1])

Zip Combine 2 lists

a=[1,2,3]

b=[4,5,6]

print(list(zip(a,b)))

Combine sublists in 1 List

m = [[1, 2, 3], [4, 5, 6]]

l=m[0]+m[1]                 #l=[1,2,3,4,5,6]

List values into string
method 1 :List into string in 1 line
   l  = [1,2,3,7]
    print ("".join([str(x) for x in l] )
method 2:
    l = [1,2,3,7]
    for i in l:
        data=data+i
    print(data)
==============Type Conversions==============
s="deepak"
s=set(list(tuple(s)))

==============Dictionary (Format similar to JSON)

d={'a':'1','b':1}                     #dictionary creation

print(d.keys() , d.values() ) #['a', 'b'][2,3]),

print( 'a' in d)                        #True (list,set,tuple,str)

print(d.items())                   #'a':'1','b':1

d[“key”]=””value”              #access individual val

==============Add 2 Dictionaries==============

Res={**d1,**d2}

==============Exchange 2 variables==============

a,b=b,a

Count occurrences in a list in 1 line using re

import re

l=[1,1,2,4,4,4]

s=set(l)

res=[ len(re.findall(str(i),str(l)))  for i in s]           # [2, 1, 3]

==============Fibnocci -0,1,1,2,3,5,8…==============

res=[0,1]

for i in range(0,5,1):

    res=res+[res[-2]+res[-1]]

print(res)

==============Unit test==============

 1.”test” suffixed for unittest class.

 2. import unittest and class under test

 3. To run untitestuse:

D:\>C:\Python34\python.exe -m unittest testfile.area_test.circle_area_test

import unittest

class area():

 def circle_area(self,r):

  return(3.14*r**2)

class area_test(unittest.TestCase):

 def circle_area_test(self):

  a=area()

  self.assertAlmostEqual(a.circle_area(0),1)

  self.assertAlmostEqual(a.circle_area(0),0)

  self.assertRaises(valueError,a.circle_area(0),0)