Python – Check for float string

Checking for float string refers to determining whether a given string can represent a floating-point number. A float string is a string that, when parsed, represents a valid float value, such as “3.14”, “-2.0”, or “0.001”.

For example:

• “3.14” is a float string.
• “abc” is not a float string.

Using try-except

try block attempts to create chunks of size k by zipping the string s into tuples and joining them. If any error occurs during this process, the except block catches it and prints an error message. For most cases, float() with exception handling is sufficient.

s = "123.45"

try:
    val = float(s)
    print("Valid float")
except ValueError:
    print("Invalid float")

Valid float

Explanation:

• try block attempts to convert the string s into a float using the float() function.
• If the conversion fails and raises a ValueError, the except block catches it and prints “Invalid float”.

Using Regular Expressions

Regular expressions can be used to check if a string matches a valid float pattern, such as "^\d+(\.\d+)?$". If the string matches, it’s considered a valid float; otherwise, it’s invalid. Use regular expressions for stricter validation or when controlling the format is necessary.

import re

s = "123.45"
pattern = r"^-?\d+\.\d+$"  # Regular expression for a valid float

if re.match(pattern, s):
    print("Valid float")
else:
    print("Invalid float")

Valid float

Explanation:

• regular expression r"^-?\d+\.\d+$" checks if the string s matches the pattern of a valid float, including optional negative signs.
• If the string matches the pattern, “Valid float” is printed; otherwise, “Invalid float” is printed.

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Article Tags :

• Python
• Python string-programs

Practice Tags :

• python