Detailed explanation of TypeError error solutions in python

Novices will encounter many pitfalls when learning python. Let’s talk about one of them in detail below.

When writing object-oriented programs in python, novices may encounter the error TypeError: this constructor takes no arguments.

For example, the following program:

class Ball:
def _init_(self,color,size,direction):
self.color=color
self.size= size
Self.direction = DIRECTION

DEF BOUNCE (SELF):
If Self.direction == "DOWN":
Self.direction = "UP"


## This myBall=Ball("red","small","down")
print "I just created a ball."
print "My ball is",myBall.size
print "My ball is" ,myBall.color
print "My ball's direction is",myBall.direction
print "Now I'm going to bounce the ball"
print
myBall.bounce()
print " Now the ball's direction is",myBall.direction

will report an error when running:

===================== == RESTART: H:\python\bounce1.py =======================

Traceback (most recent call last):
File "H:\python\bounce1.py", line 11, in
myBall=Ball("red","small","down")
TypeError: this constructor takes no arguments

The reason for the error is that the writing format of the constructor in python is __init__ instead of _init_, that is, there are double underscores on both sides of init, not a single underscore.

The modification is as follows:

class Ball:
def __init__(self,color,size,direction):
self.color=color
self.size=size
Self.direction = Direction

# DEF BOUNCE (SELF):
If Self.direction == "DOWN":
Self.direction = "UP"
## MyBall =Ball("red","small","down")
print "I just created a ball."
print "My ball is",myBall.size
print "My ball is", myBall.color
print "My ball's direction is",myBall.direction
print "Now I'm going to bounce the ball"
print
myBall.bounce()
print "Now the ball's direction is",myBall.direction

This is the correct running result:

==================== ==== RESTART: H:\python\bounce1.py =======================
I just created a ball.
My ball is small
My ball is red
My ball's direction is down
Now I'm going to bounce the ball

Now the ball's direction is up

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