Important function in python and Miscellaneous

1==1.0 is True but

0.1+0.2==0.3 is False

while(true): continue if ,break ,try,except exception as e \n print(e/customized error)

except executes after a error occurs in try # try  may/may not be printed completely

exception can be specified : except namerror:,except typerror:, valuerror:,zerodivisionerror

raise error-type("error statement")

else: gets executed if try was succcessful and no break statement

finally: gets executed irrespective of error

__name__ == __main__ by default or name of module used

import filename  , filename.funcname , from filename import variablename(or)*

global (used inside function) works on whole variable and can change its value

global- used at top of prog , defined var can be used anywhere

local -used inside a func to use that var in the func only

enumerate(iterable) # add counter to an iterable and returns it.Syntax == for index,item in enumerate(iterable)

list/set/dict comprehension == 

a=[1,2,5,1128938,3198,993,8589]

# b=[]

""" for item in a:

    if item%2==0:

        b.append(item)

"""

b=[i for i in a if i%2==0]

print(b)

dict_name={"a":3,"b":4,"A":5}

print(dict({k.lower():dict_name.get(k.lower(),0)+dict_name.get(k.upper(),0) for k in dict_name.keys()}))

newlist=[i for i in existinglist/range/input  condition]

newlist=[num*i for i in range(a,b)]

print(dict({k.lower():dict_name.get(k.lower(),0)+dict_name.get(k.upper(),0) for k in dict_name.keys()}))

list(b=[i for i in a if i%2==0])

NOTE :set comprehension is similar to list but it produces a generator object which can only be iterated once

virtual environment

lambda arguments:expressions

variable = "separation".join(list) # creates a string with elements of list separated by separation

.join(iterable object),elements should be string

format -

1. f"something {variable name}"

2. "something {index/leave empty}".format(elements)

"%s something " %(value)

map-applies a function to all elements of input_list

map(function,input_list) # function to be written without parenthesis

filter-creates a list of list for which a function returns true

filter(function,input_list) # function to be written without parenthesis

both filter and map need to be manually converted to list

from functools import reduce

val=reduce(function,input_list) # function to be written without parenthesis

reduce-applies a rolling computation to sequential pair of elements

def function_name(*args):

def function_name(**kargs):

used to take variable arguments

args and kwargs word can be replaced with anything else

args is of type tuple and kwargs is dict

dict take 1 argument at a time and kwargs take key value pair

iterable - object which can give iterator iter() or getitem()

iterator - object in which next() is defined (int not iterable)(iterable - list,tuple,string etc)

iteration - the process of iterating

yield - generates a output as an object in memory one value at a time,makes a iterator

def gen(n):

    for i in range(n+1):

        yield i

for i2 in gen(100):

    print(i2)

print(vars(object)) shows a dict with key as attributes and  values as value of arguments

generators - yield,iter 

print("%c" %(ascii code)

math.ceil(2.1)==3

math.floor(2.1)==2

import time

var=time.time()

# the above is generally used to measure the time taken by a program by defining start and end time