如何修复此 Python elif 语句语法错误？

Question

我正在尝试编写一个计算器来计算 Python 中的公式，但我的 elif 语句出现语法错误。 我已经检查了这里和其他网站上的其他几个帖子，但似乎人们犯的错误与我不同。 提前感谢您的帮助：:) 这是我的代码：

# IMPORTS

import os
import math

# SELECTION

print ("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~")
print ("~~~ PYTHAGOREAN THEOROM CALCULATOR ~~~")
print ("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~")
print ("OPTIONS:")
print ("1 - SOLVE FOR HYPOTENUSE")
print ("2 - SOLVE FOR LEG")
print ("3 - SOLVE FOR LEG 2")

user_choice = input("ENTER YOUR CHOICE: ")

# HYPOTENUSE MATHEMATICS

if user_choice == "1":
    firstnh = int(input("ENTER YOUR FIRST LEG'S DIMENSION: "))
    secondnh = int(input("ENTER YOUR SECOND LEG'S DIMENSION: "))

secondsteph = (firstnh ** 2 + secondnh **2)

hanswer = math.sqrt(secondsteph)

print (hanswer , "IS YOUR ANSWER")

input()
os.system('cls')

# LEG 1 MATHEMATICS

elif user_choice == "2":
    firstnl = int(input("ENTER YOUR LEG: "))
    secondnl = int(input("ENTER YOUR HYPOTENUSE: "))

secondstepl = (secondnl ** 2 - firstnl ** 2)

lanswer = math.sqrt(secondstepl)

print (lanswer, "IS YOUR ANSWER")

input()
os.system('cls')

错误在这里：

# LEG 1 MATHEMATICS

elif user_choice == "2":  < - - - ERROR HERE
    firstnl = int(input("ENTER YOUR LEG: "))
    secondnl = int(input("ENTER YOUR HYPOTENUSE: "))

secondstepl = (secondnl ** 2 - firstnl ** 2)

lanswer = math.sqrt(secondstepl)

print (lanswer, "IS YOUR ANSWER")

input()
os.system('cls')

这就是 IDE 所说的：

elif user_choice == "2":
    ^
SyntaxError: invalid syntax

Answer 1

问题是 if 和 elif 子句之间没有缩进的代码：

secondsteph = (firstnh ** 2 + secondnh **2)

hanswer = math.sqrt(secondsteph)

print (hanswer , "IS YOUR ANSWER")

input()
os.system('cls')

Answer 2

if 和 elif 必须在同一缩进级别：

if <condition>:
    something
elif <condition>:
    somethingelse

您不能像这样在两者之间编写代码：

if <condition>:
    something

print()
variable = "something"

elif <condition>:
    somethingelse

那么您的代码将是：

# HYPOTENUSE MATHEMATICS

if user_choice == "1":
    firstnh = int(input("ENTER YOUR FIRST LEG'S DIMENSION: "))
    secondnh = int(input("ENTER YOUR SECOND LEG'S DIMENSION: "))

    secondsteph = (firstnh ** 2 + secondnh **2)

    hanswer = math.sqrt(secondsteph)

    print (hanswer , "IS YOUR ANSWER")

    input()
    os.system('cls')

# LEG 1 MATHEMATICS

elif user_choice == "2":
    firstnl = int(input("ENTER YOUR LEG: "))
    secondnl = int(input("ENTER YOUR HYPOTENUSE: "))

    secondstepl = (secondnl ** 2 - firstnl ** 2)

    lanswer = math.sqrt(secondstepl)

    print (lanswer, "IS YOUR ANSWER")

    input()
    os.system('cls')

Answer 3

您的用法是错误的， elif语句只能在 if 语句之后使用。

if user_choice == "1":
    firstnh = int(input("ENTER YOUR FIRST LEG'S DIMENSION: "))
    secondnh = int(input("ENTER YOUR SECOND LEG'S DIMENSION: "))

这部分只在if语句中。 从secondsteph = (firstnh ** 2 + secondnh **2)行开始，它是一个新的代码块，而不是在 if 块中。 如果这是缩进错误，请尝试：

if user_choice == "1":
    firstnh = int(input("ENTER YOUR FIRST LEG'S DIMENSION: "))
    secondnh = int(input("ENTER YOUR SECOND LEG'S DIMENSION: "))

    secondsteph = (firstnh ** 2 + secondnh **2)

    hanswer = math.sqrt(secondsteph)

    print (hanswer , "IS YOUR ANSWER")

    input()
    os.system('cls')

# LEG 1 MATHEMATICS

elif user_choice == "2":
    firstnl = int(input("ENTER YOUR LEG: "))
    secondnl = int(input("ENTER YOUR HYPOTENUSE: "))

如果不是，请放置语句，

secondsteph = (firstnh ** 2 + secondnh **2)

hanswer = math.sqrt(secondsteph)

print (hanswer , "IS YOUR ANSWER")

input()
os.system('cls')

在elif块之后