如何在Python中将字符串转换为int？

How can I convert a string to an int in Python?

我的小示例应用程序的输出如下：

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Welcome to the Calculator!
Please choose what you'd like to do:
0: Addition
1: Subtraction
2: Multiplication
3: Division
4: Quit Application
0
Enter your first number: 1
Enter your second number: 1
Your result is:
11

这是因为addition()方法将input()作为字符串而不是数字。如何将它们用作数字？

这是我的整个剧本：

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def addition(a, b):
return a + b

def subtraction(a, b):
return a - b

def multiplication(a, b):
return a * b

def division(a, b):
return a / b

keepProgramRunning = True

print"Welcome to the Calculator!"

while keepProgramRunning:
print"Please choose what you'd like to do:"

print"0: Addition"
print"1: Subtraction"
print"2: Multiplication"
print"3: Division"
print"4: Quit Application"

#Capture the menu choice.
choice = raw_input()

if choice =="0":
numberA = raw_input("Enter your first number:")
numberB = raw_input("Enter your second number:")
print"Your result is:"
print addition(numberA, numberB)
elif choice =="1":
numberA = raw_input("Enter your first number:")
numberB = raw_input("Enter your second number:")
print"Your result is:"
print subtraction(numberA, numberB)
elif choice =="2":
numberA = raw_input("Enter your first number:")
numberB = raw_input("Enter your second number:")
print"Your result is:"
print multiplication(numberA, numberB)
elif choice =="3":
numberA = raw_input("Enter your first number:")
numberB = raw_input("Enter your second number:")
print"Your result is:"
print division(numberA, numberB)
elif choice =="4":
print"Bye!"
keepProgramRunning = False
else:
print"Please choose a valid option."
print"
"

相关讨论

因为您编写的计算器可能也接受浮动(1.5, 0.03)，所以更健壮的方法是使用这个简单的助手函数：

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def convertStr(s):
"""Convert string to either int or float."""
try:
ret = int(s)
except ValueError:
#Try float.
ret = float(s)
return ret

这样，如果int转换不起作用，您将得到一个float返回。

编辑：如果您不完全了解python 2.x如何处理整数除法，那么您的division函数也可能导致一些悲伤的面孔。

简而言之，如果你想让10/2等于2.5而不是2，你就需要做from __future__ import division，或者让其中一个或两个论点浮动，就像这样：

1 2	def division(a, b): return float(a) / float(b)

相关讨论

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>>> a ="123"
>>> int(a)
123

以下是一些免费代码：

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def getTwoNumbers():
numberA = raw_input("Enter your first number:")
numberB = raw_input("Enter your second number:")
return int(numberA), int(numberB)

相关讨论

从主函数调用子函数时，可以将变量转换为int，然后调用。请参考以下代码：

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import sys

print("Welcome to Calculator
")
print("Please find the options:
" +"1. Addition
" +"2. Subtraction
" +
"3. Multiplication
" +"4. Division
" +"5. Exponential
" +"6. Quit
")

def calculator():
choice = input("Enter choice
")

if int(choice) == 1:
a = input("Enter first number
")
b = input("Enter second number
")
add(int(a), int(b))

if int(choice) == 2:
a = input("Enter first number
")
b = input("Enter second number
")
diff(int(a), int(b))

if int(choice) == 3:
a = input("Enter first number
")
b = input("Enter second number
")
mult(int(a), int(b))

if int(choice) == 4:
a = input("Enter first number
")
b = input("Enter second number
")
div(float(a), float(b))

if int(choice) == 5:
a = input("Enter the base number
")
b = input("Enter the exponential
")
exp(int(a), int(b))

if int(choice) == 6:
print("Bye")
sys.exit(0)

def add(a, b):
c = a+b
print("Sum of {} and {} is {}".format(a, b, c))

def diff(a,b):
c = a-b
print("Difference between {} and {} is {}".format(a, b, c))

def mult(a, b):
c = a*b
print("The Product of {} and {} is {}".format(a, b, c))

def div(a, b):
c = a/b
print("The Quotient of {} and {} is {}".format(a, b, c))

def exp(a, b):
c = a**b
print("The result of {} to the power of {} is {}".format(a, b, c))

calculator()

我在这里做的是在将输入的参数转换为int时调用每个函数，希望这有帮助。

在您的情况下，可以这样更改：

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if choice =="0":
numberA = raw_input("Enter your first number:")
numberB = raw_input("Enter your second number:")
print"Your result is:"
print addition(int(numberA), int(numberB))

添加DEF(A、B)：返回A+B

定义减法(a，b)：返回-B

DEF倍增(A、B)：返回A*B

DEF部门(A、B)：返回A/B

keepProgramrunning=真

打印"欢迎使用计算器！"

保持编程运行时：打印"请选择要执行的操作："

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print"0: Addition"
print"1: Subtraction"
print"2: Multiplication"
print"3: Division"
print"4: Quit Application"

#Capture the menu choice.
choice = raw_input()

if choice =="0":
numberA = input("Enter your first number:")
numberB = input("Enter your second number:")
print"Your result is:" + str(addition(numberA, numberB)) +"
"
elif choice =="1":
numberA = input("Enter your first number:")
numberB = input("Enter your second number:")
print"Your result is:" + str(subtraction(numberA, numberB)) +"
"
elif choice =="2":
numberA = input("Enter your first number:")
numberB = input("Enter your second number:")
print"Your result is:" + str(multiplication(numberA, numberB)) +"
"
elif choice =="3":
numberA = input("Enter your first number:")
numberB = input("Enter your second number:")
print"Your result is:" + str(division(numberA, numberB)) +"
"
elif choice =="4":
print"Bye!"
keepProgramRunning = False
else:
print"Please choose a valid option."
print"
"

相关讨论

容易的！

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if option == str(1):
numberA = int(raw_input("enter first number."))
numberB= int(raw_input("enter second number."))
print""
print addition(numberA, numberB)
etc etc etc

也许下面，那么您的计算器就可以使用任意的基数(例如十六进制、二进制、基数7！)等)：(未测试)

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def convert(str):
try:
base = 10 # default
if ':' in str:
sstr = str.split(':')
base, str = int(sstr[0]), sstr[1]
val = int(str, base)
except ValueError:
val = None

return val

val = convert(raw_input("Enter value:"))
# 10 : Decimal
# 16:a : Hex, 10
# 2:1010 : Binary, 10

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