Preface
In Python programming,round()Functions are a very practical built-in function for rounding numbers. Whether in data processing, financial calculation or scientific calculation,round()Functions can help us get the exact value we need. This article will introduce in detailround()Usage and precautions of functions.
1. The basic syntax of the round() function
round(number, ndigits=None)
Parameter description
- number: The number to be rounded can be an integer or a floating point number.
-
ndigits: Optional parameter, specifying the number of decimal places to be retained. Default is
None, that is, return the closest integer.
Return value
- Returns the rounded value, type and input
numbersame.
2. Use examples
2.1 Round to the nearest integer
# Example 1: Rounding to the nearest integerprint(round(3.5)) # Output: 4print(round(3.2)) # Output: 3print(round(3.6)) # Output: 4
2.2 Specify the number of decimal places
# Example 2: Rounding to the specified number of decimal placesprint(round(3.14159, 2)) # Output: 3.14print(round(3.14159, 3)) # Output: 3.142print(round(2.675, 2)) # Output: 2.67 (This example will cause confusion, see the explanation below)
2.3 Rounding of negative numbers
# Example 3: Rounding negative numbersprint(round(-2.5)) # Output: -2print(round(-2.51, 1)) # Output: -2.5
2.4 Rounding integers
ifndigitsParameters are omitted,round()The function rounds the floating point number to the closest integer.
# Example 4: Rounding integersprint(round(5.9)) # Output: 6print(round(5.4)) # Output: 5
3. Things to note
3.1 Floating point accuracy problem
In some cases, the representation of floating point numbers may result in unmet results. For example:
print(round(2.675, 2)) # Output: 2.67
This situation is caused by the way floating point numbers are represented inside the computer. In order to obtain higher accuracy, it is recommended to usedecimalModule to perform accurate floating point operation.
3.2 ndigits is negative
ifndigitsis a negative number,round()The function will round the number to the decimal point on the left. For example:
# Example 5: Negative ndigitsprint(round(12345.6789, -2)) # Output: 12300.0print(round(12345.6789, -1)) # Output: 12350.0
4. Summary
round()Functions are a powerful and flexible tool in Python that can help developers easily round up numbers. By understanding its parameters and return values, and paying attention to the accuracy of floating point numbers, you can better utilize this function in your practical application.
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