Question

当我运行代码时，它给了我一个错误：在字符串格式化过程中没有转换所有参数

year = raw_input( "Please enter a year" )

if year % 4 == 0 && year % 100 != 0:
    print ( "{0} is a leap year", year )
elif year % 4 == 0 && year % 100 == 0 && year % 400 == 0:
    print ( "{0} is a leap year", year )
else:
    print ( "{0} is not a leap year", year )

Answer 1

因为raw_input返回一个字符串，所以

行

year % 4

尝试执行string format操作，该操作与模数共享相同的运算符%。

您需要使用int()将输入转换为整数。

此外，正如thefourtheye提到的那样，boolean AND operator为and，而非&&，就像C使用的那样。

所以：

while True:
    # Prompt the user until they give a valid integer.
    year = raw_input( "Please enter a year" )
    try:
        year = int(year)
        break
    except ValueError:
        pass

if (year % 4 == 0) and (year % 100 != 0):
    print "{0} is a leap year".format(year)
elif (year % 4 == 0) and (year % 100 == 0) and (year % 400 == 0):
    print "{0} is a leap year".format(year)
else:
    print "{0} is not a leap year".format(year)

使用format()注意正确的字符串格式。

Answer 2

raw_input的结果始终是一个字符串，您需要将它们显式转换为您想要的类型
```
year = int(raw_input( "Please enter a year" ))
```

在Python中，条件和运算符用and而非&&表示。

if year % 4 == 0 and year % 100 != 0:
...
elif year % 4 == 0 and year % 100 == 0 and year % 400 == 0:
...

并且，当您使用{0}时，您应该使用.format，就像这样

print ( "{0} is a leap year".format(year) )
...
print ( "{0} is a leap year".format(year) )
...
print ( "{0} is not a leap year".format(year) )

Answer 3

raw_input的输出将是一个字符串;当你使用%运算符，并且第一个操作数是一个字符串时，它会string formatting，而不是模数。（与year % 4中一样，year是一个字符串，因为它是raw_input的输出。）

简而言之，您希望year成为一个数字。你需要这样的东西：

year = int(year)

Answer 4

更改

year = raw_input( "Please enter a year" )

为：

year = int(raw_input( "Please enter a year" ))

并将每个&&替换为and

year = int(raw_input( "Please enter a year" ))

if year % 4 == 0 and year % 100 != 0:
    print ( "{0} is a leap year", year )
elif year % 4 == 0 and year % 100 == 0 and year % 400 == 0:
    print ( "{0} is a leap year", year )
else:
    print ( "{0} is not a leap year", year )

在python条件语句中使用模运算符

4 个答案: