Min, max value and index from list

See also enumerate and operator.itemgetter

import operator
a = [2, 5, 1, 4, 8, 71, 4, 1, 21]
min_i, min_v = min(enumerate(a), key = operator.itemgetter(1))
max_i, max_v = max(enumerate(a), key = operator.itemgetter(1))

print "[Min] index:",min_i,"value:",min_v
print "[Max] index:",max_i,"value:",max_v

Output:

[Min] index: 2 value: 1
[Max] index: 5 value: 71

Python: Absolute difference between successive elements in list

See also abs, zip and islice

from itertools import islice

a = [1, 4 , 2 , 6 , 7, 3]
result = [abs(p-q) for p, q in zip(a, islice(a, 1, None))]

print result

Output:

[3, 2, 4, 1, 4]

Python case insensitive dictionary

class CaseInsensitiveDict(dict):
    def __setitem__(self, key, value):
        key = key.lower()
        dict.__setitem__(self, key, value)

    def __getitem__(self, key):
        key = key.lower()
        return dict.__getitem__(self, key)

d = CaseInsensitiveDict()
d["Python"] = "Easy"
print d["PYTHON"]
print d["python"]

Output:

Easy
Easy

Python chain comparison

x = 10

print '5<x<9',5<x<9
print '5<x<11',5<x<11
print '5<x<11<10*x<101',5<x<11<10*x<101
print '10==x<90==9*x',10==x<90==9*x

Output:

5<x<9 False
5<x<11 True
5<x<11<10*x<101 True
10==x<90==9*x True

Python unpacking list, tuples or dictionary as function argument.

def my_func(a, b, c):
    print "a,b,c:",a,b,c

my_func(1,2,3)
my_func( *[1,2,3] ) # unpacking from list
my_func( *(1,2,3) ) # unpacking from tuples
my_func( **{'a':1, 'b':2, 'c':3} ) # unpacking from dictionary

Output:

a,b,c: 1 2 3
a,b,c: 1 2 3
a,b,c: 1 2 3
a,b,c: 1 2 3

Python string title - auto capitalize first character of the word

Python auto capitalize first character of all the word/words in a string.

s1 = "life is very easy with python"
s2 = "python"
print s1
print s1.title()

print s2
print s2.title()

Output:

life is very easy with python
Life Is Very Easy With Python
python
Python

Python object-class property

Python object-class property example code

class MyClass(object):
        def __init__(self, first_name, last_name):
                self.first_name = first_name
                self.last_name = last_name
        @property
        def name(self):
                return self.first_name +" "+ self.last_name


myClass = MyClass("Abu", "Zahed")
print myClass.name

Output:

Abu Zahed

date compare - code snippet

import datetime

a = datetime.date(2012,1,31) # YYYY, MM, DD
b = datetime.date(2009,10,31) # YYYY, MM, DD

print a == b
print a > b
print a < b

Output:

False
True
False

Python isinstance example

Python check an object instance using isinstance method.

class MyClass(object):
    pass

a = MyClass()
print isinstance(a,MyClass)

a = 5
print isinstance(a,MyClass)

Output:

True
False

Decorator in python

Python decorator example : Validate a function argument using decorator.

All source code available on github

from functools import wraps

def validate(func):
    @wraps(func)
    def wrapper(*args):
        for num in args:
            try:
                int(num)
            except:
                return None
        return func(*args)

    return wrapper

@validate
def add_num(*args):
    total = 0
    for num in args:
        total += num
    return total


print add_num(1,2,3)
print add_num(1,2,"asd")
print add_num(1,2,None)

Output:

6
None
None

Python implement caching - using decorator

Python custom caching using decorator.

All source code available on github

from functools import wraps

def custom_memoize(func):
    cache = {}
    @wraps(func)
    def wrapper(*args):
        if args in cache:
            print "Returning cache data"
            return cache[args]
        # If result not found then call the function
        result = func(*args)
        cache[args] = result
        return result

    return wrapper

@custom_memoize
def add(x,y):
    return x+y

print add(1,2)
print add(2,5)
print add(1,2)
print add(2,5)

Output:

3
7
Returning cache data
3
Returning cache data
7

Code snippet: Array initilize by odd number

a=[i for i in range(0,20) if i%2]
print a

Output:

[1, 3, 5, 7, 9, 11, 13, 15, 17, 19]

File read code snippet

All source code available on github

import sys

def readFile(filename):
    try:
        file = open(filename,'r')
        content = file.read()
        file.close()
        return content
    except IOError:
        print "IOError:",IOError.args[0]
    except :
        print "Unexpected error:",sys.exc_info()[0]
        raise