如何连接四舍五入数字的字符串 python？

Question

我无法找出在 python 中连接字符串的方式中的错误。

目标是将数字格式化为一个字符串，我可以用一致的长度打印它。

我写了下面的代码：

def numPrint(number,roundplace):
    num = round(number, roundplace)
    if num > 0:
        output = ('+' + str(num))
    elif num < 0:
        output = (str(num))
    else:
        output = (' 0.' + '0' * roundplace)    

    if len(output) < (3 + roundplace):
        output2 = (output + '0')
    else:
        output2 = output

    return output2

print(numPrint(0.001, 3))
print(numPrint(0, 3))
print(numPrint(-0.0019, 3))
print(numPrint(-0.01, 3))
print(numPrint(0.1, 3))

我希望它打印：

+0.001
 0.000
-0.002
-0.010
+0.100

不过，我得到了

+0.001
 0.000
-0.002
-0.010
+0.10

如何将“0”添加到最后一个以使其正常工作？

Answer 1

您可以像这样使用内置格式函数：

print("{:+.4f}".format(0.09))

在此处查看有关格式规范的更多详细信息：

https://docs.python.org/3.4/library/string.html#formatexamples

Answer 2

试试这个：


def num_print(number, roundplace):
    sign = '+' if number != 0 else ' '
    output = '{num:{sign}.{rp}f}'.format(num=number, sign=sign, rp=roundplace) # python3
#     output = f'{number:{sign}.{roundplace}f}' # python 3.6 +
    return output

+0.001
 0.000
-0.002
-0.010
+0.100

Answer 3

这会起作用：

def numPrint(number,roundplace):
    num = round(number, roundplace)
    if num > 0:
        output = ('+' + str(num))
    elif num < 0:
        output = (str(num))
    else:
        output = (' 0.' + '0' * roundplace)    

    while len(output) < (3 + roundplace): # previously you stopped after adding one trailing 0
        output = (output + '0')

    return output

print(numPrint(0.001, 3))
print(numPrint(0, 3))
print(numPrint(-0.0019, 3))
print(numPrint(-0.01, 3))
print(numPrint(0.1, 3))

Answer 4

如果只想显示数字，可以使用字符串格式。

def format_number(number, minimum_digits=1, decimal_places=2):
    format_string = '{{: {}.{}f}}'.format(minimum_digits, decimal_places)
    result = format_string.format(number)
    if number:
        result = result.replace(' ', '+', 1)  # Technically you can use '+' above but your desired output requires zero to have no sign
    return result

print(format_number(0.001, minimum_digits=1, decimal_places=3))
print(format_number(0, minimum_digits=1, decimal_places=3))
print(format_number(-0.0019, minimum_digits=1, decimal_places=3))
print(format_number(-0.01, minimum_digits=1, decimal_places=3))
print(format_number(0.1, minimum_digits=1, decimal_places=3))

+0.001
 0.000
-0.002
-0.010
+0.100

Answer 5

您只是忘了将 output2 的零相乘：

if len(output) < (3 + roundplace):
    output2 = (output + ('0'*(3 + roundplace - len(output))))
else:
    output2 = output

或者如果您不介意使用内置函数：

output2 = output.ljust(3 + roundplace, '0')

Answer 6

尝试使用 .format() 字符串方法，它非常有用和方便。

def numPrint(number,roundPlace):
   return "{{:+.{}f}}".format(roundPlace).format(number)

Answer 7

对于 Python 3.6+，您可以使用 f-string:

def num_print(number, round_place):
    return f"{number:{'+' if number else ' '}.{round_place}f}"

（我故意将您的函数名称及其第二个参数从 numPrint 和 roundPlace 更改为 num_print 和 round_place与 PEP 8 - Style Guide: Function and Variable Names.)

的一致性

如何连接四舍五入数字的字符串 python？

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