Click here to Skip to main content
15,847,263 members
Please Sign up or sign in to vote.
1.00/5 (2 votes)
See more:
Ques 1.
Python
x=+1
print(x)

Ques 2.
Python
x=12
def f1(a,b=x):
    print(a,b)
x=15
f1(4)
output:4,12


What I have tried:

I don understand the output in first question isn't it arise a name error and in 2nd question why is a =4 and b =12.
Posted
Updated 15-Feb-23 19:25pm
v2

1) Because "+" is a "dual operator" - it can work with one or two parameters.
With two, it is an addition operator:
Python
x = 3 + 3
But with one, it is a sign operator:
Python
x = +2
In this, it is matched by "-":
Python
x = 3 - 4
Python
x = -2

Unary Operators in Python | Examples of Different Operators in Python[^]
2) Because f1 is a function: it takes two parameters you pass when you call it named a and b but if you omit the second parameter it defaults to the value of x
Python Functions[^]
 
Share this answer
 
Comments
Sandeep Mewara 16-Feb-23 3:21am    
Just to add for second case, x value is not the current value that gets defaulted when called through one parameter only.
Quote:
Ques 1.
x=+1
This will always be 1 as it's an assignment not an increment.
If you do x+=1 without initializing, it will throw an error.

Quote:
Ques 2.
output:4,12

This happened as during the compiler run, value of b was already defined as 12 in sequence of code. (It is not a reference that will be updated if x changes later). For more clarity, have updated your code to show how execution happened and values of variables were being used:
Python
x=12
print('W',x)
def f1(a,b=x):
    print('X',x)
    print(a,b)
x=15
print('Y',x)
f1(4)
print('Z',x)
Output for it is:
W 12
Y 15
X 15
4 12
Z 15

You can see the value of x did change to 15 before the function call (even x value is 15 inside), but the value of b was set to 12 as it was the case when the function definition was setup in execution.
 
Share this answer
 
A1: x initial value is 0, so 0 + 1 = 1
A2: Because x is defined before the function, therefore predefined as the default value, and x = 15 is not passed to the function.
 
Share this answer
 
Comments
Sandeep Mewara 16-Feb-23 3:18am    
@Graeme - I am not entriely sure that would be the case. There is no default value of variables in python. If you try:
x = x+1 without defining x, or you do print(x) without defining, it will throw an error.
Richard Deeming 16-Feb-23 4:29am    
I suspect you're confusing =+ with += - the OP's code is assigning +1 to the variable, not adding 1 to the existing value of the variable. :)

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)



CodeProject, 20 Bay Street, 11th Floor Toronto, Ontario, Canada M5J 2N8 +1 (416) 849-8900