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3.5 Be Careful while Naming Variables
Although Python allows you to use predefined identifiers for any purpose, it is definitely a bad idea to do so because
you would lose access to Python's predefined identifiers. For example,
>>> print = 23
>>> print('Hello')
Traceback (most recent call last):
File "<pyshell#12>", line 1, in <module>
print('Hello')
TypeError: 'int' object is not callable
Note that on executing the statement:
print = 23
the identifier print refers to an integer. So, the meaning assigned to the identifier print by Python has been
overwritten. So, we are unable to print the string 'Hello' because an attempt to execute the statement
>>> print('Hello')
yields an error.
Finally, let us see some more examples of the assignment statements:
num = 10 (the variable num is assigned the value 10)
city = 'Delhi' (the variable city is assigned the string 'Delhi')
price = 150.50 (the variable price is assigned the floating-point value 150.50)
discount = 10/100*price (the variable discount is assigned the result of evaluating the
expression 10/100*price.
num 10 1000X
city "Delhi" 2000X
price 150.50 3000X
15.05
discount 4000X
(result of 10/100*150.50)
Fig 3.2: Variables and their values
To experiment with variables and their values, let us write a Python program.
Program 3.1 Playing with variables and data values
1 #Objective: To experiment with variables and their values
2 city = 'Delhi'
3 interestRate = 9.5
4 print('city =', city)
5 print('interestRate =', interestRate)
Program 3.1 has been presented in the form of two columns. While the second column comprises the lines of
Python code, the first column shows the line numbers of the Python program. The first column does not form part
of the program and is included to explain the program. The first line of the program begins with a hash character.
48 Touchpad Informatics Practices-XI

