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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 with 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 with 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

In this case, only the type is checked, so you cannot check if a float value is an integer (i.e., if the 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 float is an integer: is_integer()

float has the is_integer() method that 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 an integer number (int or integer float). This function returns False for a string (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 represents an integer

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

This function attempts to convert the value to float using float(). If the conversion is 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 details on converting strings to numbers and handling exceptions with try ... except ....

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