Master the types of Python flow control statements and learn from scratch!

To learn Python from scratch, first understand how many types of flow control statements there are!

Python is a simple and powerful programming language that is widely used in data analysis, artificial intelligence, network development and various scientific computing fields. As a beginner, it is very important to master basic flow control statements, because they are the basis for realizing logical judgment and controlling the program execution flow.

In Python, there are three main types of flow control statements: sequential structure, conditional structure and loop structure. The following will introduce these three flow control statements in detail and give corresponding code examples.

1. Sequential structure
   Sequential structure means that the program is executed in the order of the code, without interference from conditional judgments or loops. In Python, all code is executed sequentially by default. The following is a simple sequential structure code example:

print("Hello, World!")
print("Welcome to Python!")
print("Enjoy coding!")

The above code will output three lines of text in sequence: Hello, World!, Welcome to Python! and Enjoy coding!.

2. Conditional structure
   The conditional structure allows different code execution paths to be selected based on certain conditions. In Python, conditional structures are mainly implemented through if statements. The if statement determines which part of the code to execute based on whether the condition is true or false. The following is a simple conditional structure code example:

x = 10

if x > 0:
    print("x是正数")
else:
    print("x是负数或零")

The above code will output different results based on the value of x. If x is greater than 0, output "x is a positive number"; otherwise, output "x is a negative number or zero".

In addition to the if statement, Python also provides elif and else statements for processing multiple conditional judgments. The following is an example of conditional structure code with elif and else:

x = 10

if x > 0:
    print("x是正数")
elif x < 0:
    print("x是负数")
else:
    print("x是零")

The above code will output different results according to the value of x. If x is greater than 0, the output is "x is a positive number"; if x is less than 0, the output is "x is a negative number"; if x is equal to 0, the output is "x is zero".

3. Loop structure
   The loop structure allows a section of code to be executed repeatedly until a specific condition is met. In Python, there are two commonly used loop structures: for loop and while loop.

The for loop is used to traverse iterable objects (such as lists, tuples, strings, etc.) or perform a fixed number of loops. The following is a for loop code example:

fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(fruit)

The above code will output the three fruits in the list fruits: apple, banana and cherry.

The while loop is used to repeatedly execute a section of code if certain conditions are met. The following is a while loop code example:

count = 0

while count < 3:
    print("当前计数：", count)
    count += 1

The above code will output "Current Count:" and the corresponding count value three times. Each time it loops, the counter count will increase by 1 until the count is no less than 3 and the loop will stop.

By mastering the above three flow control statements, you can achieve complex logical judgment and program flow control. Of course, this is just the basic knowledge of Python process control, and there are more advanced usages and techniques waiting for you to explore and learn. Come on, learn Python from scratch, master process control, and open the door to programming!

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