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Check If a Number Is an Integer in Python

Modified: | Tags: Python, Numeric

This article explains how to check if a number is an integer or has a fractional part in Python.

Contents

See the following article to learn how to obtain the fractional and integer parts of a number.

See the following article to check if a string is a number.

Check if an object is int or float: isinstance()

You can get the type of an object using the built-in type() function.

i = 100
f = 1.23

print(type(i))
print(type(f))
# <class 'int'>
# <class 'float'>
source: check_int_float.py

You can also check if an object is of a specific type using the built-in isinstance() function.

print(isinstance(i, int))
# True

print(isinstance(i, float))
# False

print(isinstance(f, int))
# False

print(isinstance(f, float))
# True
source: check_int_float.py

Since this approach only checks the type, it cannot determine whether a float value represents an integer (i.e., whether its fractional part is 0).

f_i = 100.0

print(type(f_i))
# <class 'float'>

print(isinstance(f_i, int))
# False

print(isinstance(f_i, float))
# True
source: check_int_float.py

Check if a float value is an integer: is_integer()

The float type provides an is_integer() method, which returns True if the value is an integer and False otherwise.

f = 1.23

print(f.is_integer())
# False

f_i = 100.0

print(f_i.is_integer())
# True
source: check_int_float.py

For example, you can define a function that returns True for integer values (int or float with no fractional part). This function returns False for non-numeric types, such as strings (str).

def is_integer_num(n):
    if isinstance(n, int):
        return True
    if isinstance(n, float):
        return n.is_integer()
    return False

print(is_integer_num(100))
# True

print(is_integer_num(1.23))
# False

print(is_integer_num(100.0))
# True

print(is_integer_num('100'))
# False
source: check_int_float.py

Check if a numeric string is an integer

To check if a numeric string represents an integer value, you can use the following function.

This function attempts to convert the input to a float. If successful, it calls the is_integer() method and returns the result.

def is_integer(n):
    try:
        float(n)
    except ValueError:
        return False
    else:
        return float(n).is_integer()

print(is_integer(100))
# True

print(is_integer(100.0))
# True

print(is_integer(1.23))
# False

print(is_integer('100'))
# True

print(is_integer('100.0'))
# True

print(is_integer('1.23'))
# False

print(is_integer('string'))
# False
source: check_int_float.py

See the following articles for more details on converting strings to numbers and handling exceptions using try ... except ....

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