如何在另一个函数内部调用函数

def function1():
    print("This is function1.")

def function2():
    print("This is function2.")
    function1()  # 在function2内部调用function1

function2()

This is function2.
This is function1.

def function1():
    print("This is function1.")

def function2(func):
    print("This is function2.")
    func()  # 在function2内部调用传递进来的函数

function2(function1)

This is function2.
This is function1.

def function1():
    print("This is function1.")
    return "Hello from function1."

def function2():
    print("This is function2.")
    result = function1()  # 在function2内部调用function1并获取返回值
    print(result)

function2()

This is function2.
This is function1.
Hello from function1.