What are the common flow control structures in Python?

Master what common flow control structures are there in Python?

In Python programming, the flow control structure is a powerful tool used to control the execution sequence and conditional judgment of the program. In Python, common flow control structures include conditional statements, loop statements and exception handling statements. Let's walk through each of these constructs one by one and give concrete code examples.

1. Conditional statements (if statements):
   Conditional statements are used to execute different code blocks based on the true or false condition. In Python, the syntax of an if statement is as follows:

if <条件1>:
    <代码块1>
elif <条件2>:
    <代码块2>
else:
    <代码块3>

where the condition is an expression whose result determines which code block to execute. The following is an example:

score = 90

if score >= 90:
    print("优秀")
elif score >= 80:
    print("良好")
else:
    print("及格")

2. Loop statement:
   Loop statement can repeatedly execute a block of code until a specific condition is met to end the loop. There are two common loop statements in Python: for loop and while loop.

• for loop:
  The for loop is used to traverse an iterable object (such as a list, tuple, or string) and execute each element in it in sequence. The syntax of a for loop is as follows:

for <变量> in <可迭代对象>:
    <代码块>

The following is an example of traversing a list:

fruits = ['apple', 'banana', 'orange']

for fruit in fruits:
    print(fruit)

• while loop:
  the while loop repeatedly executes the code according to the true or false condition of the condition block until the condition is not met. The syntax of the while loop is as follows:

while <条件>:
    <代码块>

The following is an example of using a while loop to calculate the cumulative sum:

sum = 0
i = 1

while i <= 100:
    sum += i
    i += 1

print(sum)

3. Exception handling statement (try-except statement):
   Exception handling statements are used to capture and handle exceptions in the program. When an error occurs while executing code, the program stops execution and throws an exception. Use the try-except statement to handle exceptions when they occur and avoid program termination. The syntax of the exception handling statement is as follows:

try:
    <代码块>
except <异常类型>:
    <处理异常的代码块>

The following is an example of catching a division-by-zero exception:

num1 = 10
num2 = 0

try:
    result = num1 / num2
    print(result)
except ZeroDivisionError:
    print("除零错误")

Above, we introduced common flow control structures in Python, including conditional statements , loop statements and exception handling statements. Mastering these structures not only gives us better control over the execution flow of our program, but also makes our code more readable and robust. Hope this article helps you!

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