The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Use Python’s built-in float(text) for text written in Python’s numeric format. If the text includes thousands separators or locale-specific punctuation, normalize it only when the source format is known, or use locale.atof() for the active locale. Catch ValueError for invalid text and OverflowError for values outside the supported float range.
Convert an ordinary numeric string with float()
For a string in Python’s float format, pass it directly to float():
value = float(" -12.5e2 ")
print(value) # -1250.0Python documents float() as returning “a floating-point number constructed from a number or a string.” Its accepted string syntax includes leading and trailing whitespace, optional signs, decimal points, exponents, inf or infinity, nan, and underscores between digits. See the Python 3.14.7 built-in functions reference for the full grammar.
Convert strings that contain commas
A comma thousands separator is not part of the documented float() string grammar. A string such as "1,234.56" therefore needs handling before conversion.
Free tools Windows power users keep installed
One-click scans. No signup required.
#1 Best Overall
Known format: comma groups thousands, period marks decimals
If the source explicitly uses commas for grouping and periods for decimal marks, remove only the grouping commas:
text = "1,234.56"
value = float(text.replace(",", "")) # 1234.56This is safe only when that convention is established. Do not remove commas indiscriminately: in another format, a comma may be the decimal mark, and removing it would change the value.
Locale-formatted input
For text that follows the runtime’s active LC_NUMERIC convention, use locale.atof():
import locale
# Configure the intended LC_NUMERIC locale for the application first.
value = locale.atof("1.234,56")The punctuation accepted depends on the active locale; the example is not guaranteed to work unchanged on every machine. Python’s locale documentation explains that atof() delocalizes the string using locale conventions before converting it.
Recommended Free Tools
Choose the conversion method for your input
| Method | Use it when | Trade-off |
|---|---|---|
float(text) |
The input uses Python-style decimal or exponent notation. | Simple and locale-independent; grouping commas are not accepted by the documented grammar. |
Normalize, then float() |
The source uses a fixed, explicitly specified number format. | Works when the normalization matches the source; guessing at ambiguous separators can change the value. |
locale.atof(text) |
The input follows the active LC_NUMERIC convention. |
Locale-aware, but dependent on process locale configuration. |
Handle invalid or out-of-range input
Invalid numeric text raises ValueError. A value outside the range of a Python float can raise OverflowError. Handle these as input-validation failures rather than silently substituting a number:
try:
value = float(user_text)
except ValueError:
# Report or reject text that is not a valid float representation.
...
except OverflowError:
# Report a value outside the range of a Python float.
...Successful conversion does not always mean the result is an ordinary finite measurement: float() accepts nan and infinity spellings. If your application requires a finite result, check that condition after conversion.
Do not use eval() to parse numeric input
Avoid eval() for converting user-provided text. Python’s programming FAQ warns against using it for this purpose because evaluating input can be unsafe. Use float() or a format-aware parsing approach instead.
When a float is not the right representation
Binary floating-point is appropriate for many calculations, but it does not guarantee exact decimal arithmetic. If the application needs exact decimal behavior, such as for money, investigate decimal.Decimal and its input and arithmetic rules rather than assuming that successful conversion to float preserves every decimal value exactly.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
