Python3-筆記-011-函數定義與全局變量

# === 函數 ===
def function1(): # 無參函數
 print("×參數 ×返回") # 無返回

def function2(arg1, arg2): # 帶參函數(位置參數)
 return "√參數 √返回" # 有返回

def function2_1(arg1, arg2):
 return arg1, arg2 # 元組形式返回多個值

def function3(*args): # 不定長參數(位置參數),把位置參數(*args)轉成元組
 print("function3: ", args)

def function3_1(**kwargs): # 不定長參數(關鍵字參數), 把關鍵字參數(**kwargs)轉成字典
 print("function3_1: ", kwargs)

def function4(arg1 = 5): # 缺省參數(不傳參將使用默認值)(注意:Python不支持函數重載,該方式解決了重載問題)
 print("function4:%s" % arg1)

def function5(n): #遞歸示例
 "打印100以內的奇數"
 if n <= 100:
 print(n)
 n += 2
 return function5(n)


# === 位置參數 和 關鍵字參數 的混合使用 ===
def function6(arg, *args):
 print("function6: ", arg)
 print("function6: ", args)

def function7(arg, age=21, **kwargs):
 print("function7: ", arg)
 print("function7: ", age)
 print("function7: ", kwargs)

def function8(arg, age=21, *args, **kwargs): # 位置參數 只能寫在 關鍵字參數 前面
 print("function8: ", arg)
 print("function8: ", age)
 print("function8: ", args)
 print("function8: ", kwargs)


function1() # ×參數 ×返回
print(function2("a", "b")) # √參數 √返回
print(function2_1("a", "b")) # ('a', 'b')

function3(1, 2, 3) # function3: (1, 2, 3)
function3(*[1, 2, 3]) # function3: (1, 2, 3)
function3_1(a="A", b="B", c="C") # function3_1: {'a': 'A', 'b': 'B', 'c': 'C'}
function3_1(**{"a":"A", "b":"B", "c":"C"}) # function3_1: {'a': 'A', 'b': 'B', 'c': 'C'}
function4(3) # function4:3
function5(50)
function6(1, 2, 3, 4, 5)
 # function6: 1
 # function6: (2, 3, 4, 5)
function6(1, *[2, 3, 4, 5])
 # function6: 1
 # function6: (2, 3, 4, 5)
function7(1, num=12, age=50)
 # function7: 1
 # function7: 50
 # function7: {'num': 12}
function8(1, 22, 2, 3, num=12)
 # function8: 1
 # function8: 22
 # function8: (2, 3)
 # function8: {'num': 12}

# === 變量 ===
global_var = 123 # 全局變量,作用域整個程序
global_var_c = 321
def localvariable():
 local_var = 456 # 局部變量, 作用域在子程序
 global_var_c = 123 # 子程序不能修改全局變量(引用(如:list,class)除外)
 print("global_var: {}; global_var_c: {}; local_var: {}".format(global_var, global_var_c, local_var)) # => 123, 123, 456

localvariable()
print("global_var: {}; global_var_c: {}".format(global_var, global_var_c)) # => 123, 321


# === 修改全局變量 ===
global_list = {"num" : 123}
def localvariable_cg():
 global_list["num"] = 321
 print("global_list: {}".format(global_list)) # => {'num': 321}

localvariable_cg()
print("global_list: {}".format(global_list)) # => {'num': 321}


# === 修改全局變量的作死寫法 (不建議使用這種寫法, 容易造成全局變量使用混亂) ===
global_err = 123
def localvariable_err():
 global global_err
 global_err = 321
 print("global_err: {}".format(global_err)) # => 321

localvariable_err()
print("global_err: {}".format(global_err)) # => 321