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In this post, we will show you how to check if a string is a number in Python. We will use the isdigit() method to check if a string is a number.
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Introduction
Sometimes, we need to check if a string is a number. For example, we might want to validate input from a user to make sure it is numeric. Or, we might want to perform mathematical operations on a string of numbers.
In Python, there are a few ways to check if a string is a number. We can use the built-in functions int() and float(), or we can use the str.isdigit() method.
int() and float() will return ValueError if the string is not a number. So, we can use try-except to catch the error and return False if it occurs.
The str.isdigit() method returns True if the string is all digits, False otherwise. So, this is another way to check if a string is a number in Python.
Why check if a string is a number in Python?
Python’s handling of strings is inconsistent. Sometimes it tries to be helpful and automatically converts a string to a number, but other times it doesn’t. This can cause your code to break if you’re not careful.
One common scenario is when you’re reading data from a file. If the data is numeric, you might want to convert it to a float or int so you can perform mathematical operations on it. However, if the data is not numeric, you don’t want to convert it because that will cause an error.
In this case, it’s best to check if the string can be converted to a number before converting it. That way, you can handle both cases gracefully and avoid errors in your code.
The isdigit() method
In Python, isdigit() is a built-in method used for string handling.
The isdigit() method returns “True” if all characters in the string are digits, Otherwise, It returns “False”.
This function is used to check if the argument includes digits such as: “1”, “2”, “3”, etc.
However, this function also returns “True” if the argument contains special characters such as: “+”, “-“, “.” etc. For this reason, it’s recommended to use the isnumeric() method instead of isdigit().
The isnumeric() method
The isnumeric() method returns True if all the characters in a string are numeric characters. Numeric characters include digit characters and non-digit characters that can be used to form numbers. For example, the plus (+) and minus (-) signs are considered numeric characters.
If a string contains only numeric characters, then the isnumeric() method returns True, otherwise it returns False.
The isdecimal() method
In Python, the isdecimal() method is used to check whether the given string is a decimal string or not. A decimal string is a string which represents a decimal number.
The isdecimal() method takes one parameter:
str – a string to be checked
This method returns true if all characters in the string are decimal characters and there is at least one character, false otherwise.
For example, the following are all decimal strings: ‘123’, ‘-123’, ‘12.3’, ‘-12.3′ but the following are not: ’12a’, ’12-3′, ’12 3′
Comparing the three methods
There are multiple ways to check if a string is a number in Python. In this article, we will compare the three most popular methods.
The first method is to use the isdigit() method. This method returns True if all characters in the string are digits, False otherwise.
The second method is to use the isnumeric() method. This method returns True if all characters in the string are numeric, False otherwise.
The third method is to use the try/except approach. This involves trying to convert the string to a float using the float() function. If an error occurs, it means that the string is not a number and we can return False. Otherwise, we return True.
Let’s see how these methods work with some examples.
First, let’s consider a string that contains only digits:
>>> s = “12345”
>>> s.isdigit()
True
>>> s.isnumeric()
True
Other ways to check if a string is a number
Aside from using isdigit(), you can also use other ways to check if a string is a number. You can use exceptions, especially ValueError, to check if a string can be converted to a number. However, this method is not recommended as it is inefficient. Another way is to use Regular Expressions or “regex”. Regex is a sequence of characters that defines a search pattern. You can use regex to check if a string contains only numbers by using the “\d” escape character.
Conclusion
In this article, we have gone through different methods of checking if a string is a number in Python. We looked at the essentials of using the isnumeric() method as well as using exception handling to check if a string is a number.
Further reading
If you want to learn more about how to check if a string is a number in Python, there are a few resources that you can consult:
-The official Python documentation on type conversion: https://docs.python.org/3/library/stdtypes.html#typeconversions
-A tutorial on type conversion in Python: https://www.digitalocean.com/community/tutorials/how-to-convert-data-types-in-python-3
-A Stack Overflow discussion on checking if a string is a number: https://stackoverflow.com/questions/354038/how-do-i-check-if-a-string-is-‘
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References
In Python, you can use different ways to check whether a string is a number.
-You can use the `isnumeric()` method to check whether a string is a number. This method returns `True` if the string is a number, and `False` otherwise.
-You can also use the `isdecimal()` method to check whether a string is a decimal number. This method also returns `True` if the string is a decimal number, and `False` otherwise.
-If you want to check whether a string is an integer, you can use the `isinteger()` method. This method returns True if the string is an integer, and False otherwise.
-You can also use the `isdigit()` method to check if a string is a digit. This method returns True if the string is a digit, and False otherwise.
-If you want to know if a string contains only digits, you can use the `isdigit()` Method. It will return True if all characters in the string are digits and there is at least one character in it; False otherwise.”
