<opts>,<args> = getopt.getopt(argy, options, [long options]).

In dialects the parameter "skipinitialspace" is used for removing whitespaces after the delimiter. By default "skipinitialspace" has a value false. The default is False.

(i) SWIG - Simplified Wrapper Interface Generator.

(ii) MINGW – Minimalist GNU for Windows

To sort by more than one column you can use itemgetter with multiple indices: operator .itemgetter (1,2).

Syntax :

sortedlist = sorted(data,key =operator.itemgetter(Col_number),reverse-True)

Example : sortedlist = sorted (data, key operator.itemgetter(1))

(i) The next() function returns the next item from the iterator.

(ii) It can also be used to skip a row of the csv file.

The commonly used interfaces are

(i) Python-C-API(API-Application Programming Interface for interfacing with C programs)

(ii) Ctypes (for interfacing with c programs)

(iii) SWIG (Simplified Wrapper Interface Generator- Both C and C++)

(iv) Cython (Cython is both a Python-like language for writing C-extensions)

(v) Boost. Python (a framework for interfacing Python and C++)

(vi) MinGW (Minimalist GNU for Windows)

Applications of Scripting Languages :

1. To automate certain tasks in a program

2. Extracting information from a data set

3. Less code intensive as compared to traditional programming language

4. can bring new functions to applications and glue complex systems together.

Step 1: Type the c++ program in notepad and save it as with .cpp extension.

Step 2: Type the python program and save it as with .py extension

Step 3: Click the Run Terminal and open the command window

Step 4: Type the command python <program_ name.py> -i <c++ program>

(i) sys.argv is the list of command-line arguments passed to the Python program.

(ii) argv contains all the items that come along via the command-line input.

(iii) The first argument, sys.argv[0] contains the name of the python program (example pali.py)

(iv) sys.argv [1]is the next argument passed to the program.

(i) MinGW refers to a set of runtime header files, used in compiling and linking the code of C, C++ and FORTRAN to be run on Windows Operating System.

(ii) MinGw-W64 (version of MinGW) is the best compiler for C++ on Windows.
MinGW allows to compile and execute C++ program dynamically through Python program using g++.

The w' write mode creates a new file. If the file is already existing 'w mode overwrites it. Where as 'a append mode is used to add the data at the end of the file if the file already exists otherwise creates a new one.

import csv

row = ['3', ;Meena','Bangalore']

with open('student.csv', 'r', newline'=') as readFile:

reader = csv.reader(readFile)

lines = list(reader) # list()- to store each row of data as a list

lines[3]= row

with open('student.csv', 'w') as writeFile:

# returns the writer object which converts the user data with delimiter

writer = cSV.Writer(writeFile)

#writerows()method writes multiple rows to a csv file

writer.writerows(lines)

readFile.close()

writeFile.close()

Features of Python over C++:

(i) Python uses Automatic Garbage Collection whereas C ++ does not.

(ii) C ++ is a statically typed language, while Python is a dynamically typed language.

(iii) Python runs through an interpreter, while C ++ is pre-compiled.

(iv) Python code tends to be 5 to 10 times shorter than that written in C ++.

(v) In python, there is no need to declare types explicitly where as it should be done in C ++

(vi) In python, a function may accept an argument of any type, and return multiple values without any kind of declaration beforehand. Whereas in C ++ return statement can return only one value.

#Now select File → New in Notepad and type the Python program as main.py

# Program that compiles and executes a .cpp file

# Python main.py -i welcome

import sys, os, getopt

def main(argv):

cpp_file =''

exe_file = "

opts, args = getopt.getopt(argv, "i:"['ifile='])

for o, a in opts:

if o in ("-i", "--ifle"):

cpp_file =a+'.cpp'

exe file=a+'.exe'

run(cpp_file, exe_file)

def run(cpp_file, exe_file):

print("Compiling " + cpp_file)

Os.system('g++ cpp_ file +'-o'+exe_ file)

print("Running" + exe_file)

print("-------------------------'')

print

Os.system(exe_file)

print

if__name__=='__main__':

main(sys.argv[1:])

Output :

___________

Welcome

_________

import csv

csvData = [['SNO','Items'], ['1', 'Pen'], ['2','Book'], ['3', 'Pencil']]

csv.register_dialect(myDialect, delimiter = Bquotechar = "quoting=csv.QUOTE_ALL)

with open('c:\\pyprgl \chl3\\quote.csv, w) as csvFile: writer= csv.writer(csVFile, dialect-myDialect')

writer, write rows(csvData)

print("writing completed")

csvFile.close( )

When you open the "quote.csv" file in notepad, we get following output:

In the above program, myDialect uses pipe () as delimiter and quotechar as doublequote " " to write inside the file.

Read a CSV File Using Python :

There are two ways to read a CSV file.

(i) Use the csv module's reader function

(ii) Use the DictReader class.

CSV Module's Reader Function :

(i) You can read the contents of CSV file with the help of csv.reader() function. The reader function is designed to take each line of the file and make a list of all columns.

(ii) Using this function one can read data from csv files of different formats like quotes (""), pipe (|) and comma (,).

The syntax for csv.reader() is csv.reader(fileobject,delimiter,fmtparams)

where

(iii) file object : passes the path and the mode of the file

(iv) delimiter: an optional parameter containing the standard dialects like, | etc can be omitted.

(v) fmtparams: optional parameter which help to override the default values of the dialects like skipinitialspace, quoting etc. can be omitted.

Program :

#importing csv

import csv

with open(c:\pyprg\samplel.csv','r,newline'=') as F:

reader = csv.reader(F)

for row in order

print(row)

Fclose()

Output :

['SNO', 'NAME', 'CITY']

['12101', 'RAM', 'CHENNAI']

['12102', 'LAVANYA', 'TIRUCHY']

['12103', 'LAKSHMAN', 'MADURAI']

Reading CSV File Into A Dictionary :

(i) To read a CSV file into a dictionary can be done by using DictReader method of csv module which works similar to the reader() class but creates an object which maps data to a dictionary.

(ii) The keys are given by the fieldnames as parameter. DictReader works by reading the first line of the CSV and using each comma separated value in this line as a dictionary key. The columns in each subsequent row then behave like dictionary values and can be accessed with the appropriate key (i.e. fieldname).

For Example Reading "sample8.csv" file into a dictionary

import csv

filename = 'c:\pyprglsample8.csv'

input_file =csv.DictReader(open(filename:r'))

for row in input_file:

print(dict(row)) #dict() to print data

Output :

{'ItemName': 'KeyboardQuantity': '48'}

{'ItemName': 'Monitor', 'Quantity': '52'}

{'Item Name': 'Mouse','Quantity': '20'}