Python 为什么可以'；我用三个if语句代替一个if语句和两个elif语句吗？

我正在努力理解

elif

在特定代码段中的用法

在下面的复制粘贴代码中，一旦进入

while

循环，就有一个

if

语句（如果

activityToday==“Sleep”

）和两个

elif

语句（如果

activityToday==“Run”

或

activityToday==“Icecream”

分别输入）

如果我运行代码，我会得到预期的输出：

Start state: Run
Possible states: ['Run', 'Icecream', 'Run']
End state after 2 days: Run
Probability of the possible sequence of states: 0.21

Start state: Run
Possible states: ['Run', 'Run', 'Run']
End state after 2 days: Run
Probability of the possible sequence of states: 0.25

如果我将两个

elif

语句更改为两个

If

语句，我会得到一些意外的输出：

Start state: Run
Possible states: ['Run', 'Icecream', 'Run']
End state after 2 days: Run
Probability of the possible sequence of states: 0.21

Start state: Run
Possible states: ['Run', 'Run', 'Run']
End state after 2 days: Run
Probability of the possible sequence of states: 0.25

问题是我不理解意外的输出我不明白为什么我不能用两个

if

语句替换两个

elif

语句，并将它们作为三个独立的循环运行，而不是用一个

if

和两个

elif

来运行一个循环。有人能给我解释一下吗

谢谢你的帮助

import numpy as np
import random as rm

# The statespace
states = ["Sleep","Icecream","Run"]

# Possible sequences of events
transitionName = [["SS","SR","SI"],["RS","RR","RI"],["IS","IR","II"]]

# Probabilities matrix (transition matrix)
transitionMatrix = [[0.2,0.6,0.2],[0.1,0.6,0.3],[0.2,0.7,0.1]]

# FROM THE TUTORIAL 

# A function that implements the Markov model to forecast the state/mood.
def activity_forecast(days):
    # Choose the starting state
    activityToday = "Run"
    print("Start state: " + activityToday)
    # Shall store the sequence of states taken. So, this only has the starting state for now.
    activityList = [activityToday]
    i = 0
    # To calculate the probability of the activityList
    prob = 1
    while i != days:
        if activityToday == "Sleep":
            change = np.random.choice(transitionName[0],replace=True,p=transitionMatrix[0])
            if change == "SS":
                prob = prob * 0.2
                activityList.append("Sleep")
                pass
            elif change == "SR":
                prob = prob * 0.6
                activityToday = "Run"
                activityList.append("Run")
            else:
                prob = prob * 0.2
                activityToday = "Icecream"
                activityList.append("Icecream")
        elif activityToday == "Run":                            # WHY CAN'T I CHANGE 'ELIF' TO 'IF' ??????
            change = np.random.choice(transitionName[1],replace=True,p=transitionMatrix[1])
            if change == "RR":
                prob = prob * 0.5
                activityList.append("Run")
                pass
            elif change == "RS":
                prob = prob * 0.2
                activityToday = "Sleep"
                activityList.append("Sleep")
            else:
                prob = prob * 0.3
                activityToday = "Icecream"
                activityList.append("Icecream")
        elif activityToday == "Icecream":                        # WHY CAN'T I CHANGE 'ELIF' TO 'IF' ??????
            change = np.random.choice(transitionName[2],replace=True,p=transitionMatrix[2])
            if change == "II":
                prob = prob * 0.1
                activityList.append("Icecream")
                pass
            elif change == "IS":
                prob = prob * 0.2
                activityToday = "Sleep"
                activityList.append("Sleep")
            else:
                prob = prob * 0.7
                activityToday = "Run"
                activityList.append("Run")
        i += 1  
    print("Possible states: " + str(activityList))
    print("End state after "+ str(days) + " days: " + activityToday)
    print("Probability of the possible sequence of states: " + str(prob))

# Function that forecasts the possible state for the next 2 days
activity_forecast(2)

---

您无法执行此操作，因为您更改了

if

/

elif

语句中的

activityToday

的值。因此，如果没有

elif

，当

循环时，两个条件块可以在
的一次迭代中运行。
如果
如果
与
elif
相同，为什么您认为需要
elif
elif
是
else
+
if
。您正在更改if的每个分支内的
activityToday
值（即条件）。因此，在一次循环迭代中，它可能会得到多次更改如果x==1:x=2如果x==2:x=3，则x=1与如果x==1:x=2如果x==2:x=3，则x=1不相同`