Python：不是在字符串格式化时转换的所有参数 [英] Python: Not all of arguments converted during string formatting

问题描述

我正在写一个脚本，将当前的日期和时间保存为一个文件名，但我得到一个错误，指出TypeError：不是所有在字符串格式转换的参数我是Python新手，可能错过了一些明显的东西。代码如下：

Im wrtiting a script which saves the current date and time as a filename but I get an error stating "TypeError: not all arguments converted during string formatting" I am new to Python andmay of missed something obvious. Code below:

from subprocess import Popen
import datetime

today = datetime.date.today()

today = str(today)

print today

f = open("%s.sql", "w" % (today))
x =  Popen(["mysqldump", "-u", "root", "-pucsdrv", "normalisationtion"], stdout = f)
x.wait()
f.close()

推荐答案

字符串格式错误的地方;它需要正确的格式化后的字符串：

You're putting the string formatting in the wrong place; it needs to be right after the string that's being formatted:

f = open("%s.sql" % (today), "w")

合法的是不传递格式参数，就像％s.sql，但传递参数并不合法（w％（today）传递一个，但是在w中没有字符串格式，所以你得到一个错误，并不是所有的参数都被使用了）

It's legal to not pass any formatting arguments, like you did with "%s.sql", but it's not legal to pass arguments but not the right amount ("w" % (today) passes one, but there's no string formatting in "w", so you get an error that not all of the arguments were used)

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