Python 解析时出现意外的 EOF
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Unexpected EOF while parsing
提问by Moath Wafeeq
Objectives: I need to read cost and discount rate and number of year and calculate the time adjusted cost and time adjusted benefits and cumulative for both.
目标：我需要阅读成本和折扣率以及年数，并计算两者的时间调整成本和时间调整收益以及累积。
I receive this error:
我收到此错误：
Traceback (most recent call last):
File "D:\python\codetest\hw.py", line 3, in <module>
cost = eval(input("Enter Development cost :"))
File "<string>", line 0
^
SyntaxError: unexpected EOF while parsing
When I remove evalthe code works fine.
当我删除eval代码时工作正常。
#import numpy as np
cost = eval(input("Enter Development cost :"))
discrate = eval(input("Enter discount rate :"))
#operation cost list
opcost = []
#benifits list
benifits = []
#dicount rate list
#dicount rate list
discount=[]
#time adjusted cost
TAC = []
#time adjusted benifits
TAB = []
CTAC=[]
year = eval(input("Enter number of year "))
for i in range (year):
opcost.append(eval(input("Enter operation cost :")))
for i in range (year):
benifits.append(eval(input("Enter benifit for this year :")))
for i in range (year):
pvn = (1/pow(1+discrate,i))
# print (pvn)
discount.append(pvn)
for i in range (year):
TAC.append(discount[i] * opcost[i])
#print(TAC[i])
for i in range(year):
TAB.append(discount[i] * benifits[i]))
#CTAC = np.cumsum(TAC)
#for i in range (year):
# print(CTAC[i])
采纳答案by Martijn Pieters
When you use eval(), Python tries to parse the string you pass to it as a Python expression. You passed in an empty string:
当您使用 时eval()，Python 会尝试解析您作为 Python 表达式传递给它的字符串。您传入了一个空字符串：
>>> eval('')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 0
^
SyntaxError: unexpected EOF while parsing
Rather than use eval()you should use a specific converter; if your costs are floating point values then use float()instead:
eval()您应该使用特定的转换器而不是使用；如果您的成本是浮点值，请float()改用：
opcost.append(float(input("Enter operation cost :")))
This can still cause errors if the user just hits ENTERand you get another empty string:
如果用户刚刚点击ENTER并且您得到另一个空字符串，这仍然会导致错误：
>>> float('')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not convert string to float:
You can still handle that case by catching the exception. See Asking the user for input until they give a valid responsefor more details on how to best do this, including how to handle repeatedly asking until valid input is given.
您仍然可以通过捕获异常来处理这种情况。有关如何最好地执行此操作的更多详细信息，请参阅询问用户输入直到他们给出有效响应，包括如何处理重复询问直到给出有效输入。
