Summary: Use the isinstance(var, int) method to check if a variable is an Integer or not. The method checks if a specified object is of a specified type or not. Another method to check if the variable is an integer or not is the is_integer() function which checks if a given float variable holds an integer value or a decimal value.
Problem: Given a variable in a program; how to check if it is an integer or not?
def checInt(val): #Some function to check if val is an Integer #if YES: return True #else return False a = 25 b = 'FINXTER' print(checInt(a)) print(checInt(b))
Thus, in the above example we need to define a procedure such that when we check if
a is an integer then it returns
True while for
b it should return
? Before proceeding further, let me give you a teaser of the solutions that are lined up next. Please have a look at the code given below.
def checInt(val): # Method 1 if (isinstance(val,(int,float)) == True): print ("Method 1 Successful!") # Method 2 if (val.is_integer): print ("Method 2 Successful!") # Method 3 if (val == round(val)): print ("Method 3 Successful!") # Method 4 if (val % 1 == 0): print ("Method 4 Successful!") a = 25.0 checInt(a)
Method 1 Successful! Method 2 Successful! Method 3 Successful! Method 4 Successful!
Now, without further delay let us discuss the various methods to get our desired output.
Method 1: Using isinstance(var, int)
isinstance is a built-in method in Python which returns
True when the specified object is an instance of the specified type, otherwise it returns
# Example 1 class Finxter: name = "Python" obj = Finxter() test = isinstance(obj, Finxter) print(test) # Example 2 x = isinstance("Hello Finxter!", (str,float,int)) print(x)
Now that we know about the
isinstance method, let us check how we can use it to check if the variable is integer or not. Please follow the program given below:
class Finxter(int): pass x = Finxter(0) print(isinstance(x, int))
Why We Should Not use “type”?
The usage of type to solve our problem should be avoided because if you subclass
int as in the above example,
type won’t register the value of the variable as int. Let us have a look at the following piece of code to understand, why using
type is not a good option.
class Test(int): pass x = Test(0) print(type(x) == int) # False print(type(x),"is not same as int")
False <class '__main__.Test'> is not same as int
✍ A probable workaround for the above issue could be the usage of
subclass() which is a built-in function in Python that checks if a given class/object is a subclass of another specified class. Let us have a look at this in a program given below:
class Test(int): pass x = Test(0) print(issubclass(type(x), int))
Method 2: Using var.is_integer()
An integer represents only an integer value (no decimal), while float represents numbers that can be integers like 25.0 as well as decimal numbers like 25.75. We can thus call the
is_integer() method to check if the float represents an integer.
Let us have a look at the following to get a clear picture.
a = 25.0 b = 25.75 print(a.is_integer()) print(b.is_integer())
Method 3: Using round()
A simple approach to check if the given variable is an integer or not can be to check if it is equal to the value when it is rounded. For this purpose, we can use the in-built
round() method in Python which returns the nearest integer when no values are passed on to the optional
numberrepresents the number that has to be rounded.
digitsrepresent the number of decimals to be used while rounding the number.
Let’s have a look at the following program to check if a variable is an integer or not:
def is_int(value): if value == round(value): print ('True') else: print ('False') a = 25.0 b = 25.75 is_int(a) is_int(b)
Method 4: A Quick Hack
Here’s a quick hack to check if the given variable is an integer or not. All we need is a simple modulo operator as shown below.
def is_int(value): if value%1 == 0 : print ('True') else: print ('False') a = 25.0 b = 25.75 is_int(a) is_int(b)
Caution: This just a quick workaround and should not be considered as a first choice while checking if a variable is an integer or not.
Method 5: Using try And except Block
Another approach to our problem is to use the
except block. Instead of directly checking if the value is an integer or not, we consider it to be an integer initially and catch the exception if it isn’t. If this sounds confusing, please have a look at the program below which will make things easy for you.
def is_int(value): try: return int(value)==value except ValueError: return False a = 25.0 b = 25.75 c = "FINXTER" print(is_int(a)) print(is_int(b)) print(is_int(c))
True False False
Method 6: Using str.isdigit() Method
If you want to check if a variable has an integer string value or not, then the
str.isdigit() method can be very useful. As the name suggests,
True if all the characters present in the string are digits. Otherwise, it returns
- It only works if the str is string. Integers do not have an
Falsefor negative integers
Now, let us have a look at a working example of the
isdigit() method to check if a variable is an integer string or not.
def is_int(value): return str.isdigit(value) a = "25" b = "FINXTER" print(is_int(a)) print(is_int(b))
The key points that we learned in this article were:
- Using the
typeshould be avoided in solving our problem.
- Using the
- Using the
- Using the round() function.
exceptblocks to solve our problem.
- Using the
Where to Go From Here?
Enough theory. Let’s get some practice!
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