Python Argv - 字符串转换为整数
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Argv - String into Integer
提问by Andrew Blanchette
I'm pretty new at python and I've been playing with argv. I wrote this simple program here and getting an error that says :
我在 python 方面很新，我一直在玩 argv。我在这里编写了这个简单的程序并收到一个错误消息：
TypeError: %d format: a number is required, not str
类型错误：%d 格式：需要一个数字，而不是 str
from sys import argv
file_name, num1, num2 = argv
int(argv[1])
int(argv[2])
def addfunc(num1, num2):
print "This function adds %d and %d" % (num1, num2)
return num1 + num2
addsum = addfunc(num1, num2)
print "The final sum of addfunc is: " + str(addsum)
When I run filename.py 2 2, does argv put 2 2 into strings? If so, how do I convert these into integers?
当我运行 filename.py 2 2 时，argv 是否将 2 2 放入字符串中？如果是这样，我如何将这些转换为整数？
Thanks for your help.
谢谢你的帮助。
采纳答案by Martijn Pieters
sys.argvis indeed a list of strings. Use the int()function to turn a string to a number, provided the string canbe converted.
sys.argv确实是一个字符串列表。使用该int()函数将字符串转换为数字，前提是该字符串可以转换。
You need to assignthe result, however:
但是，您需要分配结果：
num1 = int(argv[1])
num2 = int(argv[2])
or simply use:
或简单地使用：
num1, num2 = int(num1), int(num2)
You did call int()but ignored the return value.
您确实调用了int()但忽略了返回值。
回答by Ashwini Chaudhary
Assign the converted integers to those variables:
将转换后的整数分配给这些变量：
num1 = int(argv[1]) #assign the return int to num1
num2 = int(argv[2])
Doing just:
只做：
int(argv[1])
int(argv[2])
won't affect the original items as intreturns a new intobject, the items inside sys.argvare not affected by that.
不会影响原始项目，因为int返回一个新int对象，里面的项目sys.argv不受此影响。
Yo modify the original list you can do this:
哟修改原始列表你可以这样做：
argv[1:] = [int(x) for x in argv[1:]]
file_name, num1, num2 = argv #now num1 and num2 are going to be integers
回答by J David Smith
Running int(argv[1])doesn't actually change the value of argv[1](or of num1, to which it is assigned).
运行int(argv[1])实际上并没有改变argv[1](或 of num1，它被分配到) 的值。
Replace this:
替换这个：
int(argv[1])
int(argv[2])
With this:
有了这个：
num1 = int(num1)
num2 = int(num2)
and it should work.
它应该工作。
The int(..), str(...) etc functions do not modify the values passed to them. Instead, they returna reinterpretation of the data as a different type.
int(..)、str(...) 等函数不会修改传递给它们的值。相反，它们将数据的重新解释返回为不同的类型。
