default value of argument in python when no argument given at all: arg1 = new

def happyBirthday(FirstName="FN", LastName="LN"):
    print("Happy Birthday, dear " + FirstName + " " + LastName + ".")
   
happyBirthday()
  
Will print: Happy Birthday, dear FN LN.

happyBirthday("FN1"): will print Will print: Happy Birthday, dear FN1 LN.
happyBirthday("FN1", "LN1"): will print Will print: Happy Birthday, dear FN1 LN1.

Function in python

def happyBirthday(person):
    print("Happy Birthday, dear " + person + ".")

Note: parenthesis is must to : A. define a function, B. use a function

def a():

   print("a")

a()

variable length argument in Python: **kw

http://pythontips.com/2013/08/04/args-and-kwargs-in-python-explained/

http://stackoverflow.com/questions/287085/what-do-args-and-kwargs-mean

Old Python : it is not necessary to write *args or **kwargs. Only the * (aesteric) is necessary. You could have also written *var and **vars. Writing *args and **kwargs is just a convention. So now lets take a look at *args first.

New Python: * and ** are different

Usage of *args
*args and **kwargs are mostly used in function definitions. *args and **kwargs allow you to pass a variable number of arguments to a function. What does variable mean here is that you do not know before hand that how many arguments can be passed to your function by the user so in this case you use these two keywords. *args is used to send a non-keyworded variable length argument list to the function.

if __name__ == "__main__" : Usage

http://stackoverflow.com/questions/419163/what-does-if-name-main-do

__name__ == "__main__"  is set when the module runs directly and is set to module name when an imported module is running at the time of call.

python programming techniques

date time in python

>>> datetime.datetime.now().time()

http://stackoverflow.com/questions/415511/how-to-get-current-time-in-python

from datetime import datetime
print("time=" + str(datetime.now()))
 

Create/Overwrite file

#providing name for the file to be created
filename = raw_input("Give name for the file: ")
target = open (filename, 'a') ## a will append, w will over-write 
#providing the content for the file
print "provide three lines of content for the file:"
line1 = raw_input("line 1: ")
line2 = raw_input("line 2: ")
line3 = raw_input("line 3: ")
#writing the entered content to the file we just created
print "entered three lines are written to the file"
target.write(line1)
target.write("n")
target.write(line2)
target.write("n")
target.write(line3)
target.write("n")
#providing information that writing task is completed
print "we have added those text to the file"
target.close()