Python ValueError：解包的值太多（预期为 2）
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ValueError: too many values to unpack (expected 2)
提问by Ziggy
In the Python tutorial book I'm using, I typed an example given for simultaneous assignment. I get the aforementioned ValueError when I run the program, and can't figure out why.
在我正在使用的 Python 教程书中，我输入了一个用于同时分配的示例。运行程序时出现上述 ValueError，但不知道为什么。
Here's the code:
这是代码：
#avg2.py
#A simple program to average two exam scores
#Illustrates use of multiple input
def main():
print("This program computes the average of two exam scores.")
score1, score2 = input("Enter two scores separated by a comma: ")
average = (int(score1) + int(score2)) / 2.0
print("The average of the scores is:", average)
main()
Here's the output.
这是输出。
>>> import avg2
This program computes the average of two exam scores.
Enter two scores separated by a comma: 69, 87
Traceback (most recent call last):
File "<pyshell#4>", line 1, in <module>
import avg2
File "C:\Python34\avg2.py", line 13, in <module>
main()
File "C:\Python34\avg2.py", line 8, in main
score1, score2 = input("Enter two scores separated by a comma: ")
ValueError: too many values to unpack (expected 2)
回答by Ziggy
Judging by the prompt message, you forgot to call str.splitat the end of the 8th line:
从提示信息来看，你忘记str.split在第8行末尾调用：
score1, score2 = input("Enter two scores separated by a comma: ").split(",")
# ^^^^^^^^^^^
Doing so splits the input on the comma. See a demonstration below:
这样做会拆分逗号上的输入。请参阅下面的演示：
>>> input("Enter two scores separated by a comma: ").split(",")
Enter two scores separated by a comma: 10,20
['10', '20']
>>> score1, score2 = input("Enter two scores separated by a comma: ").split(",")
Enter two scores separated by a comma: 10,20
>>> score1
'10'
>>> score2
'20'
>>>
回答by shaktimaan
The above code will work fine on Python 2.x. Because inputbehaves as raw_inputfollowed by a evalon Python 2.x as documented here - https://docs.python.org/2/library/functions.html#input
上面的代码在 Python 2.x 上可以正常工作。因为input作为的行为raw_input，随后由eval有关Python 2.x的作为记录在这里- https://docs.python.org/2/library/functions.html#input
However, above code throws the error you mentioned on Python 3.x. On Python 3.x you can use the astmodule's literal_eval()method on the user input.
但是，上面的代码会引发您在 Python 3.x 上提到的错误。在 Python 3.x 上，您可以在用户输入上使用ast模块的literal_eval()方法。
This is what I mean:
这就是我的意思：
import ast
def main():
print("This program computes the average of two exam scores.")
score1, score2 = ast.literal_eval(input("Enter two scores separated by a comma: "))
average = (int(score1) + int(score2)) / 2.0
print("The average of the scores is:", average)
main()
回答by DexJ
This is because behavior of input changed in python3
这是因为输入的行为在 python3 中发生了变化
In python2.7 input returns value and your program work fine in this version
在 python2.7 输入返回值，你的程序在这个版本中工作正常
But in python3 input returns string
但是在python3中输入返回字符串
try this and it will work fine!
试试这个，它会工作得很好！
score1, score2 = eval(input("Enter two scores separated by a comma: "))
回答by X.Na
that means your function return more value!
这意味着您的函数返回更多值！
ex:
前任：
in python2 the function cv2.findContours()return --> contours, hierarchy
在python2中函数cv2.findContours()返回-->contours, hierarchy
but in python3 findContours(image, mode, method[, contours[, hierarchy[, offset]]]) -> image, contours, hierarchy
但是在python3中 findContours(image, mode, method[, contours[, hierarchy[, offset]]]) -> image, contours, hierarchy
so when you use those function, contours, hierachy = cv2.findContours(...)is well by python2, but in python3 function return 3 value to 2 variable.
因此，当您使用这些函数时，contours, hierachy = cv2.findContours(...)python2 很好，但是在 python3 函数中，将 3 个值返回到 2 个变量。
SO ValueError: too many values to unpack (expected 2)
SO ValueError：解包的值太多（预期为 2）
