How to check if a string contains only digits using Python's isdigit() function

How to use Python's isdigit() function to check whether a string only contains digits

In Python, we often need to check whether a string only contains digits. This happens frequently in data processing, text analysis, and input validation. Python's built-in isdigit() function is a tool used to determine whether a string only contains numbers.

The isdigit() function is a method of the Python string object. It returns a Boolean value indicating whether the string contains only numeric characters. The following is the basic syntax for using the isdigit() function:

result = string.isdigit()

Among them, string is the string to be checked, result is the returned result, if the string is only If it contains numeric characters, result is True, otherwise it is False.

The following are some specific examples of using the isdigit() function:

1. Check whether the string only contains digits:

string1 = "12345"
string2 = "hello123"
print(string1.isdigit())  # 输出: True
print(string2.isdigit())  # 输出: False

Running results:

True
False

2. Implement a function to verify whether the user input is a valid age:

def validate_age(age):
    if age.isdigit() and 0 < int(age) <= 120:
        return True
    else:
        return False

age1 = "25"
age2 = "abc"
age3 = "150"
print(validate_age(age1))  # 输出: True
print(validate_age(age2))  # 输出: False
print(validate_age(age3))  # 输出: False

Running result:

True
False
False

In the above example, we use isdigit () function and other logical conditions to verify whether the age entered by the user is valid. If the user input is a non-negative integer between 1 and 120 (inclusive), then True is returned; otherwise, False is returned.

It should be noted that the isdigit() function can only check whether the string consists only of digits. It cannot recognize negative numbers, decimals, exponential notation and other special characters. For example, "-123", "3.14", "1.5e10" and "$123" all fail the isdigit() function's check.

To sum up, the isdigit() function is a quick and easy way to check whether a string contains only numeric characters. By combining other logical conditions, we can use the isdigit() function to implement custom string validation and processing logic. However, you need to pay attention to its scope of application in application to avoid incorrect judgments when using it.

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