字符串切片是否？

Question

这个学期在Python上开设了一个课程，目前的作业遇到了麻烦。 直到现在为止，通过课堂上完成的示例和练习，仍然找不到任何东西。

Q1）固定

aN = raw_input("Enter a number with decimals")
bN = raw_input("Enter a binary number, 2 to 4 digits in length")

if (bN[-1] == 1):
    print "The binary number was odd so your number will contain 2 decimals"
    print "The number is now",aN[0:4],

elif (bN[-1] == 0):
    print "The binary number was even so your number will contain 1 decimal"
    print "The number is now",bN[0:3]

我希望它能够打印出两个语句，每个结果一个。 如果输入的二进制数字以“ 1”结尾，它将以2个小数点吐出aN；如果输入的二进制数字以“ 0”结尾，则将以1个小数点吐出aN。

它运行时，在显示用户为bN输入的值后，它什么也不做

Q2）是否有更好的方法来查找小数点后的数字？ 切片仅在数字<10时有效。

编辑）对那个指出字符串的人，我完全忘记了:(

aN = raw_input("Enter a number with decimals")
bN = raw_input("Enter a binary number, 2 to 4 digits in length")

if (float(bN[-1]) == 1):
    print "The binary number was odd so your number will contain 2 decimals"
    print "The number is now",aN[0:4],

elif (float(bN[-1]) == 0):
    print "The binary number was even so your number will contain 1 decimal"
    print "The number is now",aN[0:3]

如果有人可以回答第二个问题，那就太好了。

Answer 1

raw_input()将输入作为字符串。 在您的if条件中，您正在编译一个带有整数的字符串。 让你if这样，

if float(bN[-1]) == 1:
    print "The binary number was odd so your number will contain 2 decimals"
    print "The number is now %.2f" % float(aN)

elif float(bN[-1]) == 0:
    print "The binary number was even so your number will contain 1 decimal"
    print "The number is now", bN[0:3]

如果要在小数点后打印两位数，则可以采用这种方法。

Answer 2

首先， raw_input()将输入作为str 。

因此，将aN[-1]与int任何比较都会导致False 。 即您的代码将始终运行else块。

此外，您需要首先找到小数点的索引，然后计算是显示一个还是两个位置（或者处理没有小数点的情况）

aN = raw_input("Enter a number with decimals")
bN = raw_input("Enter a binary number, 2 to 4 digits in length")

if (bN[-1] == '1'):
    print "The binary number was odd so your number will contain 2 decimals"
    if aN.find('.') == -1:
        print "The number is now ",aN
    else:
        print "The number is now ", aN[:aN.find('.')+3]

elif (bN[-1] == '0'):
    print "The binary number was even so your number will contain 1 decimal"
    if aN.find('.') == -1:
        print "The number is now ",aN
    else:
        print "The number is now ", aN[:aN.find('.')+2]

Answer 3

假设aN总是至少有1个小数，这应该是可行的。 您可以使用find()找到“”。 小数点。

aN = raw_input("Enter a number with decimals")
bN = raw_input("Enter a binary number, 2 to 4 digits in length")

if (bN[-1] == "1"):
    print "The binary number was odd so your number will contain 2 decimals"
    print "The number is now", aN[:aN.find(".")+3]

elif (bN[-1] == "0"):
    print "The binary number was even so your number will contain 1 decimal"
    print "The number is now", aN[:aN.find(".")+2]

例：

>>> aN
'1.12345'
>>> bN
'11'
>>> if (bN[-1] == "1"):
...     print "The binary number was odd so your number will contain 2 decimals"
...     print "The number is now", aN[:aN.find(".")+3]
... elif (bN[-1] == "0"):
...     print "The binary number was even so your number will contain 1 decimal"
...     print "The number is now", aN[:aN.find(".")+2]
...
The binary number was odd so your number will contain 2 decimals
The number is now 1.12