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Python Keywords and Identifiers
  • Difficulty Level : Easy
  • Last Updated : 16 Feb, 2021

The keywords are some predefined and reserved words in python that have special meaning. Keywords are used to define the syntax of the coding. The keyword cannot be used as an identifier, function, and variable name. All the keywords in python are written in lower case expect True and False. There are 33 keywords in Python 3.7 let’s go through all of them one by one.

Total Python keywords

No.    Keywords                                                                                    Description
1 and This is a logical operator it returns true if both the operands are true else return false.
2 Or This is also a logical operator it returns true if anyone operand is true else return false.
3 not This is again a logical operator it returns True if the operand is false else return false.
4 if This is used to make a conditional statement.
5 elif Elif is a condition statement used with if statement the elif statement is executed if the previous conditions were not true
6 else Else is used with if and elif conditional statement the else block is executed if the given condition is not true.
7 for This is created for a loop.
8 while This keyword is used to create a while loop.
9 break This is used to terminate the loop.
10 as This is used to create an alternative.
11 def It helps us to define functions.
12 lambda It used to define the anonymous function.
13 pass This is a null statement that means it will do nothing.
14 return It will return a value and exit the function.
15 True This is a boolean value.
16 False This is also a boolean value.
17 try It makes a try-except statement.
18 with The with keyword is used to simplify exception handling.
19 assert This function is used for debugging purposes. Usually used to check the correctness of code
20 class It helps us to define a class.
21 continue It continues to the next iteration of a loop
22 del It deletes a reference to an object.
23 except Used with exceptions, what to do when an exception occurs
24 finally Finally is use with exceptions, a block of code that will be executed no matter if there is an exception or not.
25 from The form is used to import specific parts of any module.
26 global This declares a global variable.
27 import This is used to import a module.
28 in It’s used to check if a value is present in a list, tuple, etc, or not.
29 is This is used to check if the two variables are equal or not.
30 None This is a special constant used to denote a null value or avoid. It’s important to remember, 0, any empty container(e.g empty list) do not compute to None
31 nonlocal It’s declared a non-local variable.
32 raise This raises an exception
33 yield It’s ends a function and returns a generator.

Identifiers: The identifier is a name used to identify a variable, function, class, module, etc. The identifier is a combination of character digits and underscore. The identifier should start with a character or Underscore then use digit. The characters are A-Z or a-z,a UnderScore ( _ ) and digit (0-9). we should not use special characters ( #, @, $, %, ! ) in identifiers.

Examples of valid identifiers:

  1. var1
  2. _var1
  3. _1_var
  4. var_1

Examples of invalid identifiers

  1. !var1
  2. 1var
  3. 1_var
  4. var#1

Example 1: Example of and, or, not, True, False keywords.



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print("example of True, False, and, or not keywords")
 
#  compare two operands using and operator
print(True and True)
 
# compare two operands using or operator
print(True or False)
 
# use of not operator
print(not False)

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Output:

example of True, False, and, or not keywords
True
True
True

Example 2: Example of a break, continue.

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# execute for loop
for i in range(1, 11):
     
    # print the value of i
    print(i)
     
    # check the value of i is less then 5
    # if i lessthen 5 then continue loop
    if i < 5
        continue
         
    # if i greather then 5 then break loop
    else
        break

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Output:

1
2
3
4
5

Example 3: example of for, in, if, elif and else keyword.

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# run for loop
for t in range(1, 5):
  # print one of t ==1
    if t == 1:
        print('One')
   # print two if t ==2
    elif t == 2:
        print('Two')
    else:
        print('else block execute')

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Output:

One
Two
else block execute
else block execute

Example 4: Example of def, if and else keywords.

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# define GFG() function using def keyword
def GFG():
    i=20
    # check i is odd or not
    # using if and else keyword
    if(i % 2 == 0):
        print("given number is even")
    else:
        print("given number is odd")   
     
# call GFG() function   
GFG()

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Output:

given number is even

Example 5: example try, except, raise.



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def fun(num):
    try:
        r = 1/num
    except:
        print('Exception raies')
        return
    return r
 
print(fun(10))
print(fun(0))

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Output:

0.1
Exception raies
None

Example 6: Example of a lambda keyword.

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# define a anonymous using lambda keyword
# this labda function increment the value of b
a = lambda b: b+1
 
# run a for loop
for i in range(1, 6):
    print(a(i))

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Output:

2
3
4
5
6

Example 7: use of return keyword.

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# define a function
def fun():
  # declare a variable
    a = 5
    # return the value of a
    return a
# call fun method and store
# it's return value in a variable 
t = fun()
# print the value of t
print(t)

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Output:

5

Example 8: use of a del keyword.

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# create a list
l = ['a', 'b', 'c', 'd', 'e']
 
# print list before using del keyword
print(l)
 
del l[2]
 
# print list after using del keyword
print(l)

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Output:

['a', 'b', 'c', 'd', 'e']
['a', 'b', 'd', 'e']

Example 9: use of global keyword.

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# declare a variable
gvar = 10
 
# create a function
def fun1():
  # print the value of gvar
    print(gvar)
 
# declare fun2()
def fun2():
  # declare global value gvar
    global gvar
    gvar = 100
 
# call fun1()
fun1()
 
# call fun2()
fun2()

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Output:

10

Example 10: example of yield keyword.

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def Generator():
    for i in range(6):
        yield i+1
 
t = Generator()
for i in t:
    print(i)

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Output:

1
2
3
4
5
6

Example 10: example of assert keyword.

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def sumOfMoney(money):
    assert len(money) != 0,"List is empty."
    return sum(money)
 
money = []
print("sum of money:",sumOfMoney(money))

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Output:

AssertionError: List is empty.

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