[英]Why adding try except block in if statement and the program says variable not defined
[英]Using a Try and Except block, but in the Except Part it says Not Defined Python
我的代码将华氏温度转换为摄氏温度。 就是这个。
def again():
calc = raw_input("Press y to convert again. Press n to quit. ").lower()
if calc == "y":
main()
elif calc == "n":
quit()
else:
again()
def main():
fahrenheit = input("What do you want to convert from Fahrenheit to Celsius? ")
try:
celsius = (fahrenheit - 32) *5 / float(9)
print('%0.2F degree Celsius is equal to about %0.1f degree Fahrenheit' %(celsius,fahrenheit))
again()
except ValueError:
print("That is not a number")
check()
如果您运行它,然后键入字母而不是数字进行转换。 它不执行Except位,但表示未定义字母。 如果我执行了fahrenheit = input("What do you want to convert from Fahrenheit to Celsius? ")
,我将如何使用Try位将引号中的数字转换为不带引号的普通数字? 我认为这是因为我选择了Value Error
但我不知道。 任何帮助,将不胜感激!
当您执行fahrenheit - 32
,您的代码尝试从字符串中减去整数,这将导致以下异常:
TypeError: unsupported operand type(s) for -: 'str' and 'int'
这不是ValueError
,所以它不会被您的except
子句捕获。
如果要捕获ValueError
,则需要在您的try:
块中放入fahrenheit = int(fahrenheit)
。
您正在使用python 2.x,而不是3.x。 在python 2.x中,您需要使用raw_input
,而不是input
。 所以改变这个:
fahrenheit = input(
"What do you want to convert from Fahrenheit to Celsius? ")
对此:
fahrenheit = raw_input(
"What do you want to convert from Fahrenheit to Celsius? ")
运行显示input()
在python 2.7中失败:
C:\Python27\python.exe test.py
What do you want to convert from Fahrenheit to Celsius? d
Traceback (most recent call last):
...
"What do you want to convert from Fahrenheit to Celsius? ")
File "<string>", line 1, in <module>
NameError: name 'd' is not defined
使用python 3.5运行显示input()
:
"C:\Program Files (x86)\Python35-32\python.exe" test.py
What do you want to convert from Fahrenheit to Celsius? d
Traceback (most recent call last):
...
File "C:/Users/stephen/Documents/src/testcode/test.py", line 31, in main
celsius = (fahrenheit - 32) * 5 / float(9)
TypeError: unsupported operand type(s) for -: 'str' and 'int'
运行显示raw_input()
使用python 2.7:
C:\Python27\python.exe test.py awk_data.txt
What do you want to convert from Fahrenheit to Celsius? d
Traceback (most recent call last):
...
File "C:/Users/stephen/Documents/src/testcode/test.py", line 31, in main
celsius = (fahrenheit - 32) * 5 / float(9)
TypeError: unsupported operand type(s) for -: 'str' and 'int'
尝试将用户的输入转换为整数,如下所示:
fahrenheit = int(fahrenheit)
如果您使用的是python 3.x,则应为最终代码
def again():
calc = input("Press y to convert again. Press n to quit. ").lower()
if calc == "y":
main()
elif calc == "n":
quit()
else:
again()
def main():
fahrenheit = input("What do you want to convert from Fahrenheit to Celsius? ")
try:
fahrenheit = int(fahrenheit)
celsius = (fahrenheit - 32) *5 / float(9)
print('%0.2F degree Celsius is equal to about %0.1f degree Fahrenheit' %(celsius,fahrenheit))
again()
except ValueError:
print("That is not a number")
#check()
main()
希望能帮助到你
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