python。print float 两位小数 python 如何控制输出的小数长度？
python\u6d6e\u70b9\u578b\u4fdd\u7559\u4e24\u4f4d\u5c0f\u65701\u3001\u4f7f\u7528\u5b57\u7b26\u4e32\u683c\u5f0f\u5316
\u5927\u90e8\u5206\u8bed\u8a00\u90fd\u53ef\u4ee5\u4f7f\u7528\u5b57\u7b26\u4e32\u683c\u5f0f\u5316\u7684\u65b9\u6cd5\u6765\u5b9e\u73b0\u4fdd\u7559\u4e24\u4f4d\u5c0f\u6570\uff0cPython\u4e5f\u4e0d\u4f8b\u5916\u3002
a = 12.345
print("%.2f" % a) #%\u4ee3\u8868\u683c\u5f0f\u5316\u8f93\u51fa\uff0c.2\u4ee3\u8868\u5c0f\u6570\u70b9\u540e\u4fdd\u7559\u4e24\u4f4d\uff0cf\u4ee3\u8868\u6570\u636e\u7c7b\u578b\u662f\u6d6e\u70b9\u578b
2\u3001\u4f7f\u7528round\u5185\u7f6e\u51fd\u6570
Python\u5185\u7f6e\u4e86\u4e00\u4e2a\u540d\u4e3around\u7684\u51fd\u6570\uff0c\u8fd9\u4e2a\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u5bf9\u6570\u636e\u8fdb\u884c\u683c\u5f0f\u5316\u3002
a = 12.345
a1 = round(a,2) #\u5c06a\u901a\u8fc7round\u51fd\u6570\u5904\u7406\u540e\u8d4b\u503c\u7ed9a1\uff0c\u4f20\u5165\u76842\u4ee3\u8868\u4fdd\u7559\u4e24\u4f4d\u5c0f\u6570
print(a1)
3\u3001\u4f7f\u7528decimal\u6a21\u5757
\u7c7b\u4f3c\u4e8eJava\uff0cPython\u4e5f\u4e13\u95e8\u63d0\u4f9b\u4e86\u4e00\u4e2adecimal\u6a21\u5757\u7528\u4e8e\u7cbe\u786e\u8fd0\u7b97\uff0c\u5b83\u4e5f\u53ef\u4ee5\u8fdb\u884c\u6570\u636e\u7684\u683c\u5f0f\u5316\u8f93\u51fa\u3002
from decimal import Decimal
a = 12.345
Decimal(a).quantize(Decimal("0.00")) # \u4f7f\u7528\u9ed8\u8ba4\u7684\u8fdb\u4f4d\u65b9\u5f0f(\u540cround)"0.00"\u8868\u793a\u4fdd\u7559\u5c0f\u6570\u70b9\u540e\u4e24\u4f4d
\u6ce8\u610f\uff1aPython\u7684round\u91c7\u7528\u7684\u8fdb\u4f4d\u65b9\u5f0f\u6bd4\u8f83\u7279\u6b8a\uff0c\u6709\u70b9\u7c7b\u4f3c\u4e8e\u56db\u820d\u4e94\u5165\uff0c\u4f46\u51c6\u786e\u7684\u6765\u8bf4\u5e94\u8be5\u53eb\u56db\u820d\u516d\u5165\u4e94\u6210\u53cc\u3002
\u4ee5\u4e0a\u5c31\u662f\u5e38\u89c4\u7684\u4fdd\u7559\u4e24\u4f4d\u5c0f\u6570\u7684\u65b9\u6cd5\uff0c\u63a5\u4e0b\u6765\u4ecb\u7ecd\u4e24\u79cd\u975e\u5e38\u89c4\u7684\u65b9\u6cd5\u3002
4\u3001\u4f7f\u7528\u5e8f\u5217\u5207\u7247
\u539f\u7406\u5f88\u7b80\u5355\uff0c\u53ea\u8981\u627e\u5230\u5c0f\u6570\u70b9\uff0c\u7136\u540e\u8fdb\u884c\u5207\u7247\u5373\u53ef\u3002
a = 12.345
str(a).split('.')[0] + '.' + str(a).split('.')[1][:2] #\u4f7f\u7528\u5e8f\u5217\u5207\u7247\u7684\u65b9\u5f0f\uff0c\u5207\u51fa\u5c0f\u6570\u70b9\u524d\u7684\u6570\u636e\uff0c\u8fd8\u6709\u5c0f\u6570\u70b9\u540e\u4e24\u4f4d\u7684\u6570\u636e\uff0c\u7136\u540e\u8fdb\u884c\u62fc\u88c5
5\u3001\u4f7f\u7528re\u6a21\u5757
\u7c7b\u4f3c\u4e8e\u5207\u7247\uff0c\u4e0d\u8fc7\u8fd9\u6b21\u4f7f\u7528\u6b63\u5219\u5339\u914d\u6765\u5b9a\u4f4d\u5c0f\u6570\u70b9\u4f4d\u7f6e\u3002
import re
a = 12.345
re.findall(r"\d{1,}?\.\d{2}", str(a)) #\u4f7f\u7528\u6b63\u5219\u5339\u914d\uff0c\u5c06\u7b26\u5408\u89c4\u5219\u5b57\u7b26\u4e32\u7247\u6bb5\u53d6\u51fa
\u3000\u3000Python\u91cc\u9762\u5c0f\u6570\u70b9\u957f\u5ea6\u7cbe\u5ea6\u63a7\u5236\u65b9\u6cd5\uff1a
\u3000\u3000\u4e00\u3001\u8981\u6c42\u8f83\u5c0f\u7684\u7cbe\u5ea6
\u3000\u3000\u5c06\u7cbe\u5ea6\u9ad8\u7684\u6d6e\u70b9\u6570\u8f6c\u6362\u6210\u7cbe\u5ea6\u4f4e\u7684\u6d6e\u70b9\u6570\u3002
\u3000\u30001.round()\u5185\u7f6e\u65b9\u6cd5
\u3000\u3000\u8fd9\u4e2a\u662f\u4f7f\u7528\u6700\u591a\u7684\uff0c\u521a\u770b\u4e86round()\u7684\u4f7f\u7528\u89e3\u91ca\uff0c\u4e5f\u4e0d\u662f\u5f88\u5bb9\u6613\u61c2\u3002round()\u4e0d\u662f\u7b80\u5355\u7684\u56db\u820d\u4e94\u5165\u7684\u5904\u7406\u65b9\u5f0f\u3002
\u3000\u3000For the built-in types supporting round(), values are rounded to the
closest multiple of 10 to the power minus ndigits; if two multiples are equally
close, rounding is done toward the even choice (so, for example, both round(0.5)
and round(-0.5) are 0, and round(1.5) is 2).
\u3000\u3000>>> round(2.5)
\u3000\u30002
\u3000\u3000>>> round(1.5)
\u3000\u30002
\u3000\u3000>>> round(2.675)
\u3000\u30003
\u3000\u3000>>> round(2.675, 2)
\u3000\u30002.67
\u3000\u3000round()\u5982\u679c\u53ea\u6709\u4e00\u4e2a\u6570\u4f5c\u4e3a\u53c2\u6570\uff0c\u4e0d\u6307\u5b9a\u4f4d\u6570\u7684\u65f6\u5019\uff0c\u8fd4\u56de\u7684\u662f\u4e00\u4e2a\u6574\u6570\uff0c\u800c\u4e14\u662f\u6700\u9760\u8fd1\u7684\u6574\u6570(\u8fd9\u70b9\u4e0a\u7c7b\u4f3c\u56db\u820d\u4e94\u5165)\u3002\u4f46\u662f\u5f53\u51fa\u73b0.5\u7684\u65f6\u5019\uff0c\u4e24\u8fb9\u7684\u8ddd\u79bb\u90fd\u4e00\u6837\uff0cround()\u53d6\u9760\u8fd1\u7684\u5076\u6570\uff0c\u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48round(2.5)
=
2\u3002\u5f53\u6307\u5b9a\u53d6\u820d\u7684\u5c0f\u6570\u70b9\u4f4d\u6570\u7684\u65f6\u5019\uff0c\u4e00\u822c\u60c5\u51b5\u4e5f\u662f\u4f7f\u7528\u56db\u820d\u4e94\u5165\u7684\u89c4\u5219\uff0c\u4f46\u662f\u78b0\u5230.5\u7684\u8fd9\u6837\u60c5\u51b5\uff0c\u5982\u679c\u8981\u53d6\u820d\u7684\u4f4d\u6570\u524d\u7684\u5c0f\u6811\u662f\u5947\u6570\uff0c\u5219\u76f4\u63a5\u820d\u5f03\uff0c\u5982\u679c\u5076\u6570\u8fd9\u5411\u4e0a\u53d6\u820d\u3002\u770b\u4e0b\u9762\u7684\u793a\u4f8b\uff1a
\u3000\u3000>>> round(2.635, 2)
\u3000\u30002.63
\u3000\u3000>>> round(2.645, 2)
\u3000\u30002.65
\u3000\u3000>>> round(2.655, 2)
\u3000\u30002.65
\u3000\u3000>>> round(2.665, 2)
\u3000\u30002.67
\u3000\u3000>>> round(2.675, 2)
\u3000\u30002.67
\u3000\u30002. \u4f7f\u7528\u683c\u5f0f\u5316
\u3000\u3000\u6548\u679c\u548cround()\u662f\u4e00\u6837\u7684\u3002
\u3000\u3000>>> a = ("%.2f" % 2.635)
\u3000\u3000>>> a
\u3000\u3000'2.63'
\u3000\u3000>>> a = ("%.2f" % 2.645)
\u3000\u3000>>> a
\u3000\u3000'2.65'
\u3000\u3000>>> a = int(2.5)
\u3000\u3000>>> a
\u3000\u30002
\u3000\u3000\u4e8c\u3001\u8981\u6c42\u8d85\u8fc717\u4f4d\u7684\u7cbe\u5ea6\u5206\u6790
\u3000\u3000python\u9ed8\u8ba4\u7684\u662f17\u4f4d\u5c0f\u6570\u7684\u7cbe\u5ea6\uff0c\u4f46\u662f\u8fd9\u91cc\u6709\u4e00\u4e2a\u95ee\u9898\uff0c\u5c31\u662f\u5f53\u6211\u4eec\u7684\u8ba1\u7b97\u9700\u8981\u4f7f\u7528\u66f4\u9ad8\u7684\u7cbe\u5ea6(\u8d85\u8fc717\u4f4d\u5c0f\u6570)\u7684\u65f6\u5019\u8be5\u600e\u4e48\u505a\u5462?
\u3000\u30001. \u4f7f\u7528\u683c\u5f0f\u5316(\u4e0d\u63a8\u8350)
\u3000\u3000>>> a = "%.30f" % (1/3)
\u3000\u3000>>> a
\u3000\u3000'0.333333333333333314829616256247'
\u3000\u3000\u53ef\u4ee5\u663e\u793a\uff0c\u4f46\u662f\u4e0d\u51c6\u786e\uff0c\u540e\u9762\u7684\u6570\u5b57\u5f80\u5f80\u6ca1\u6709\u610f\u4e49\u3002
\u3000\u30002. \u9ad8\u7cbe\u5ea6\u4f7f\u7528decimal\u6a21\u5757\uff0c\u914d\u5408getcontext
\u3000\u3000>>> from decimal import *
\u3000\u3000>>> print(getcontext())
\u3000\u3000Context(prec=28, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999,
capitals=1, clamp=0, flags=[], traps=[InvalidOperation, DivisionByZero,
Overflow])
\u3000\u3000>>> getcontext().prec = 50
\u3000\u3000>>> b = Decimal(1)/Decimal(3)
\u3000\u3000>>> b
\u3000\u3000Decimal('0.33333333333333333333333333333333333333333333333333')
\u3000\u3000>>> c = Decimal(1)/Decimal(17)
\u3000\u3000>>> c
\u3000\u3000Decimal('0.058823529411764705882352941176470588235294117647059')
\u3000\u3000>>> float(c)
\u3000\u30000.058823529411764705
\u3000\u3000\u9ed8\u8ba4\u7684context\u7684\u7cbe\u5ea6\u662f28\u4f4d\uff0c\u53ef\u4ee5\u8bbe\u7f6e\u4e3a50\u4f4d\u751a\u81f3\u66f4\u9ad8\uff0c\u90fd\u53ef\u4ee5\u3002\u8fd9\u6837\u5728\u5206\u6790\u590d\u6742\u7684\u6d6e\u70b9\u6570\u7684\u65f6\u5019\uff0c\u53ef\u4ee5\u6709\u66f4\u9ad8\u7684\u81ea\u5df1\u53ef\u4ee5\u63a7\u5236\u7684\u7cbe\u5ea6\u3002\u5176\u5b9e\u53ef\u4ee5\u7559\u610f\u4e0bcontext\u91cc\u9762\u7684\u8fd9rounding=ROUND_HALF_EVEN
\u53c2\u6570\u3002ROUND_HALF_EVEN\uff0c \u5f53half\u7684\u65f6\u5019\uff0c\u9760\u8fd1even.
\u3000\u3000\u4e09\u3001\u5173\u4e8e\u5c0f\u6570\u548c\u53d6\u6574
\u3000\u3000\u65e2\u7136\u8bf4\u5230\u5c0f\u6570\uff0c\u5c31\u5fc5\u7136\u8981\u8bf4\u5230\u6574\u6570\u3002\u4e00\u822c\u53d6\u6574\u4f1a\u7528\u5230\u8fd9\u4e9b\u51fd\u6570\uff1a
\u3000\u30001. round()
\u3000\u3000\u8fd9\u4e2a\u4e0d\u8bf4\u4e86\uff0c\u524d\u9762\u5df2\u7ecf\u8bb2\u8fc7\u4e86\u3002\u4e00\u5b9a\u8981\u6ce8\u610f\u5b83\u4e0d\u662f\u7b80\u5355\u7684\u56db\u820d\u4e94\u5165\uff0c\u800c\u662fROUND_HALF_EVEN\u7684\u7b56\u7565\u3002
\u3000\u30002. math\u6a21\u5757\u7684ceil(x)
\u3000\u3000\u53d6\u5927\u4e8e\u6216\u8005\u7b49\u4e8ex\u7684\u6700\u5c0f\u6574\u6570\u3002
\u3000\u30003. math\u6a21\u5757\u7684floor(x)
\u3000\u3000\u53bb\u5c0f\u4e8e\u6216\u8005\u7b49\u4e8ex\u7684\u6700\u5927\u6574\u6570\u3002
\u3000\u3000>>> from math import ceil, floor
\u3000\u3000>>> round(2.5)
\u3000\u30002
\u3000\u3000>>> ceil(2.5)
\u3000\u30003
\u3000\u3000>>> floor(2.5)
\u3000\u30002
\u3000\u3000>>> round(2.3)
\u3000\u30002
\u3000\u3000>>> ceil(2.3)
\u3000\u30003
\u3000\u3000>>> floor(2.3)
\u3000\u30002
\u3000\u3000>>>
#方法1：
print("%.2f" % 0.13333)
#方法2
print("{:.2f}".format(0.13333))
#方法3
round(0.13333, 2)
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