以下是我在Python 2.7中构建的简单Mils到Degrees转换计算器的（半）完成版本作为学习练习。我是Python新手，仍在解决问题。前提是，用户选择将mils转换为度数，反之亦然。用户输入所选单位的方位角，并将其转换为另一个单位。如果用户选择了无效的菜单选项，则会通知他。如果他进入范围之外的方位角（1-360度，mils为1-6400），他会收到通知，必须重新开始。问题是如果用户输入无效方位角，比如365度，他就会被踢回菜单。 有没有办法在if / else循环中返回上一步？我搜索了论坛和文档，但似乎不可能。此外，由于我是Python的新手，如何才能使这段代码更高效？ 我是否需要在函数定义中使用 if 和 elif 语句，还是可以将它们组合而不会产生错误或冗余输出？我是没有成功这样做。欢迎并赞赏所有意见。
#Mil-Deg.py
#Simple Mils / Degrees Conversion Calculator
#6 JAN 2013
#Note: 6400 mils / 360 degrees in a circle. 17.78 mils to one degree.
import sys
import math
import winsound
#Define menu function
def menu():
print
print " Mils / Degrees Conversion Calculator"
print "-" * 38
print
print "Options: "
print "1. Degrees to Mils"
print
print "2. Mils to Degrees"
print
print "3. Quit"
print "-" * 20
print
return input ("Choose your option: ")
print
#Define mils to degrees function
def m2d(a):
if a <= 6400 and a >= 1: #get user input within given range
b = 17.78
c = round((a / b),0) #convert and round to nearest degree
if c > 359 or c < 1: #change 0 degrees to 360
c = 360
#Output
print
print a, "mils =", int (c), "degrees"
else:
print
print a, "mils =", int (c), "degrees"
elif a > -1 and a < 1: #change 0 mils to 6400
a = 6400
b = 17.78
c = round((a / b), 0) #math, same as above
if c > 359 or c < 1: #0 to 360, same as above
c = 360
#Output
print
print 6400, "mils =", int (c), "degrees"
else:
print
print a, "mils =", int (c), "degrees"
else:
#warning, mulligan
winsound.Beep(440, 500)
print
print "*** There are only 6400 mils in a circle. Try again. ***"
print
print "-" * 38
print
#define degrees to mils function
def d2m(b):
if b <= 360 and b > 0: #get user input within given range
a = 17.78
c = round((b * a),0) #convert and round to nearest mil
if c >= 6400: #set limit to 6400 mils
c = 6400
#Output
print
print b, "degrees =", int (c), "mils"
else:
print
print b, "degrees =", int (c), "mils"
elif b > -1 and b < 1: #change 0 to 360 degrees
b = 360
a = 17.78
c = round((b * a),0) #math, same as above
if c >= 6400:
c = 6400
#Output
print
print 360, "degrees =", int (c), "mils"
else:
print
print b, "degrees =", int (c), "mils"
else:
#warning
winsound.Beep(440, 500)
print
print "*** There are only 360 degrees in a circle. Try again. ***"
print
print "-" * 38
print
#Begin program
loop = 1
choice = 0
while loop == 1:
choice = menu() #Menu function call
if choice == 1: #If user chooses degrees to mils:
#Output
print
print "Enter your azimuth in degrees (1 - 360)"
print
d2m(input("Degrees: ")) #function call
elif choice == 2: #If user chooses mils to degrees:
#Output
print
print "Enter your azimuth in mils (1 - 6400)"
print
m2d(input("Mils: ")) #function call
elif choice == 3: #If user chooses quit, exit program
loop = 0
elif choice != 1 and choice != 2 and choice != 3: #if user makes invalid menu choice:
#warning
winsound.Beep(440, 500)
print
print
print
print choice, "is not a valid choice."
print
print "Please choose from the available options."
print
print
print
print "-" * 38
print
print "Thank you for using Mil-Deg.py"
print
print
答案 0 :(得分：0)
正如Ashwini在评论中提到的，你的if-else条件块实际上并不是一个循环，因此使用while循环应该回答你问题的程序流程部分。
就elif和一般的优雅而言，考虑this method of handling multiple options using a dictionary of functions;这里肯定没有必要使用你的一些选项，但它可能会让你练习Python如何处理字典和函数作为类。
在风格上，我建议使用换行符转义序列\n而不是所有这些无关的打印语句。
答案 1 :(得分：0)
我稍微清理了你的代码并进行了以下更改：
format函数来轻松打印计算。结果如下：
import sys
import math
import winsound
#Define menu function
def menu():
'''This function prints the main menu''' # this is a docstring for your method
print "\nMils / Degrees Conversion Calculator"
print "-" * 38
print "\nOptions: "
print "1. Degrees to Mils\n"
print "2. Mils to Degrees\n"
print "3. Quit\n"
print "-" * 20
print "\n"
#Define mils to degrees function
def mils_to_degrees(a): # use method names that make sense
'''This function takes mils and converts them into degrees'''
b = 17.78
c = round((a / b),0) #convert and round to nearest degree
if c > 359 or c < 1: #change 0 degrees to 360
c = 360
return (a,int(c))
#define degrees to mils function
def degrees_to_mils(b):
'''This method converts degrees to mils'''
a = 17.78
if b == 0:
b = 360
c = round((b * a),0) #math, same as above
if c > 6400: #set limit to 6400 mils
c = 6400
return (b,c)
def check_input(user_input):
'''Checks if the input is a number'''
try:
converted_number = int(user_input)
except ValueError:
return -1
return converted_number
#Begin program
loop = True
while loop:
menu()
choice = int(raw_input("Choose your option: "))
if choice not in [1,2,3]:
winsound.Beep(440, 500)
print choice, "is not a valid choice.\n"
print "Please choose from the available options.\n"
menu()
choice = int(raw_input('Choose your option: '))
if choice == 1:
print "\nEnter your azimuth in degrees (0 - 360)\n"
degrees = check_input(raw_input('Degrees: '))
if degrees > 360 or degrees < 0:
print 'Please enter a value between 0 and 360'
else:
result = degrees_to_mils(degrees) # function call
print '{} degrees = {} mils'.format(*result)
print "-" * 38
elif choice == 2: #If user chooses mils to degrees:
print "\nEnter your azimuth in mils (1 - 6400)\n"
mils = check_input(raw_input('Mils: '))
if mils > 6400 or mils < 1:
print 'Please enter a value between 1 and 6400'
else:
result = mils_to_degrees(mils) #function call
print '{} mils = {} degrees'.format(*result)
print "-" * 38
elif choice == 3:
loop = False
print "\n"
print "-" * 38
print "\nThank you for using Mil-Deg.py\n\n"