在 Python 中出现错误“SyntaxWarning: 'str' object is not callable”

问题
我正在学习 Python，我发现了一个错误，在网上搜索了一下，但我仍然不明白为什么。 我做错了什么？

代码：

1. length = float(input("please input the length: "))
   
2. unit = input("please input the unit: ")
   
3. if unit == "in" or "inch":
   
4.     length_b = float(length / 2.54)
   
5.     print("%f inch = %f cm"(length, length_b))
   
6. elif unit == "cm":
   
7.     length_b = float(length * 2.54)
   
8.     print("%f cm = %f inch"(length, length_b))
   
9. else:
   
10.     print("calculation failed")

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我犯了一个错误：

1. test.py:143: SyntaxWarning: 'str' object is not callable; perhaps you missed a comma?
   
2.   print("%f inch = %f cm"(length, length_b))
   
3. test.py:146: SyntaxWarning: 'str' object is not callable; perhaps you missed a comma?
   
4.   print("%f cm = %f inch"(length, length_b))

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回答
您必须在打印的报告中使用 %，如下所示：

1. length = float(input("please input the length: "))
   
2. unit = input("please input the unit: ")
   
3. if unit == "in" or unit == "inch":
   
4.     length_b = float(length / 2.54)
   
5.     print("%f inch = %f cm"%(length, round(length_b,6)))
   
6. elif unit == "cm":
   
7.     length_b = float(length * 2.54)
   
8.     print("%f cm = %f inch"%(length, round(length_b,6)))
   
9. else:
   
10.     print("calculation failed")

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附加：您可以使用 format() 函数轻松尝试：

1. length = float(input("please input the length: "))
   
2. unit = input("please input the unit: ")
   
3. if unit == "in" or unit == "inch":
   
4.     length_b = float(length / 2.54)
   
5.     print("inch is {} and cm is {}".format(length, length_b))
   
6. elif unit == "cm":
   
7.     length_b = float(length * 2.54)
   
8.     print("cm is {} and inch is {}".format(length, length_b))
   
9. else:
   
10.     print("calculation failed")

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输出：

1. please input the length: 5
   
2. please input the unit: in
   
3. inch is 5.0 and cm is 1.968504

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(problem
I'm learning python. I found an error and searched the Internet, but I still don't understand why. What did I do wrong?
code:

1. length = float(input("please input the length: "))
   
2. unit = input("please input the unit: ")
   
3. if unit == "in" or "inch":
   
4. length_ b = float(length / 2.54)
   
5. print("%f inch = %f cm"(length, length_b))
   
6. elif unit == "cm":
   
7. length_ b = float(length * 2.54)
   
8. print("%f cm = %f inch"(length, length_b))
   
9. else:
   
10. print("calculation failed")

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I made a mistake:

1. test. py:143: SyntaxWarning: 'str' object is not callable;  perhaps you missed a comma?
   
2. print("%f inch = %f cm"(length, length_b))
   
3. test. py:146: SyntaxWarning: 'str' object is not callable;  perhaps you missed a comma?
   
4. print("%f cm = %f inch"(length, length_b))

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answer
You must use% in the printed report as follows:

1. length = float(input("please input the length: "))
   
2. unit = input("please input the unit: ")
   
3. if unit == "in" or unit == "inch":
   
4. length_ b = float(length / 2.54)
   
5. print("%f inch = %f cm"%(length, round(length_b,6)))
   
6. elif unit == "cm":
   
7. length_ b = float(length * 2.54)
   
8. print("%f cm = %f inch"%(length, round(length_b,6)))
   
9. else:
   
10. print("calculation failed")

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Additional: you can easily try using the format() function:

1. length = float(input("please input the length: "))
   
2. unit = input("please input the unit: ")
   
3. if unit == "in" or unit == "inch":
   
4. length_ b = float(length / 2.54)
   
5. print("inch is {} and cm is {}".format(length, length_b))
   
6. elif unit == "cm":
   
7. length_ b = float(length * 2.54)
   
8. print("cm is {} and inch is {}".format(length, length_b))
   
9. else:
   
10. print("calculation failed")

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Output:

1. please input the length: 5
   
2. please input the unit: in
   
3. inch is 5.0 and cm is 1.968504

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