Command line arguments

argv is not Array it is a list. It is available sys Module 

The argument which are passing at the time of execution are called command line Arguments.

Eg: D:\Python_classes py test.py   10(command) 20(line) 30(arguments)

Within the python program this command line arguments are available in argv. Which is present in SYS module.

Test.py

10

20

30

Note: 

             argv[0]  represents Name of program. But not first command line argument.

             argv[1] represents first command line argument

Program : To check type of argv from sys 

import  argv

print(type(argv))

D:\Python_classes\py test.py

Write a program to display command line arguments 

from sys import argv

print(“The Number of Command Line Arguments:”, len(argv))

print(“The List of Command Line Arguments:”,argv)

print(“Command Line Arguments one by one:”)

for x in argv 

     print(x)

D:\Python_classes>py test.py 10 20 30 

The Number of Command Line Arguments: 4 

The List of Command Line Arguments: [’test.py’, ’10’,’20’,’30’]

Command Line Arguments one by one 

test.py

10

20

30

---

from sys import argv

sum=0

args=argv[1:]

for x in args :

 n=int(x)

sum=sum+n

print(”The Sum:”,sum)

D:\python_classes>py test.py 10 20 30 40 

The Sum: 100

Note1: Usually space is separator b/w command line arguments. If our command line arguments. If our command line argument itself contains space then we should enclose within double quotes(but not single quotes )

from  sys import argv 

print(argv[1])

D:\Python_classes>py test.py Karthik Bear 

Karthik 

D:\Python_classes>py test.py 'Karthik Bear’

‘Karthik 

D:\Python_classes>py test.py "Karthik Bear"

Karthik Bear 

Note2: within the python program command line arguments are available in the string form. Based on our requirement, we can convert into corresponding type by using type casting methods.

from  sys import argv

print(argv[1]+argv[2])

print(int(argv[1])+int(argv[2]))

D:\Python_classes>py test.py 10 20 

1020

30 

Note3:  If we are trying to access command line arguments with out of range index then we will get error.

1. from sys import argv
2. print(argv[100])

D:\Python_classes>py test.py 10 20 

IndexError: list index out of range.

Note : In python there is argparse module to parse command line arguments and display some help messages whenever end user enters  wrong inputs.

Input

raw_input 

Command line arguments 

Output statements 

We can print() function to display output 

Form1 : print() without any argument 

Just in prints new line character

Form2: 

print(String):

print(“Hello World”)

We can use escape characters also 

print(“Hello \n World”)

print(“Hello\tWorld”)

We can use repetition operator (*) in the string

print(10*”Hello”)

print(“Hello”*10)

We can use + operator also 

print(“Hello”+”World”)

Note: 

If both arguments are string type then  + operator acts as concatenation operator.

If one argument is string type and second is any other type like int then we will get error 

If both arguments are number type then + operator acts as arithmetic addition operator 

Note:

print(“Hello”+”World”)

print(“Hello”,”World”)

HelloWorld

Hello World 

Form3: print() with variable number of arguments 

> a,b,c=10,20,30 

> print(a,b,c,sep=‘,’)

> print(a,b,c,sep=‘:’)

D:\Python_classes>py test.py

10,20,30

10:20:30

Form4: print() with end attribute 

print(“Hello”)

print(“Good”)

print(“Morning”)

Output 

Hello 

Good 

Morning 

If we want output in the same line with space.

print(“Hello”,end=‘’)

print(“karthik”,end=‘’)

print(“world”)

output: Hello Karthik World 

Note: The default value for end attribute is \n, which is nothing but new line character.

Form5: print(object) statement

We can pass any object ( like list, tuple, set etc ) as argument to the print() statement

I=[10,20,30,40]

t=(10,20,30,40)

print(I)

Print(t)

Form6: print(String, variable list)

We can use print() statement with string and any number of arguments

s=“karthik”

a=48

s1=“Java”

s2=“Python”

print(“Hello”,s,”Your Age is”,a)

print(“You are teaching”,s1,”and”,s2)

Output 

Hello Karthik Your Age is 48 

You are teaching java and python 

Form-7: print (formatted string)

1. %I —> int
2. %d —> int
3. %f —> float 
4. %s —> String type 

Syntax: print(“formatted string” %(variable list))

a=10

b=20

c=30

print(“a value is %I” %a)

print(“b value is %d and  c value is %d” %(b,c))

Output

a value is 10

b value is 20 and c value is 30 

Eg2: 

s=“Karthik”

list=[10,20,30,40]

print(“Hello %s….. The list of items are  %s” %(s,list))

Output : 

Hello karthik…. The list of items are  [10,20,30,40]

Form-8: print() with replacement operator {} 

Eg: 

name = “Karthik”

salary = 10000

gf = “Sunny”

print(“Hello {0} your salary is {1} and Your Friend {2} is waiting”.format(name, salary,gf))

print(“Hello {x} your salary is {y} and Your Friend {z} is waiting”.format(x=name, y=salary,z=gf))

Output 

Hello Karthik your salary is 10000 and Your Friend Sunny is waiting 

Hello Karthik your salary is 10000 and Your Friend Sunny is waiting