自定義函數(shù)及調(diào)用

創(chuàng)建一個(gè)專(zhuān)門(mén)存放自定義函數(shù)的文件夾 D:\python\customize

構(gòu)建一個(gè)簡(jiǎn)單的函數(shù)

def greet_user():          # 關(guān)鍵詞 def 開(kāi)頭，后接定義的函數(shù)名肺然，括號(hào)必不可少辉饱，最后以冒號(hào)結(jié)尾 
    '''顯示簡(jiǎn)單的問(wèn)候語(yǔ)'''    # 注釋用三個(gè)引號(hào)括起
    print('Hello!')        # 單引號(hào)雙引號(hào)都可以

將函數(shù)保存到 customize 文件夾中已骇，命名為greet.py

image-20211114002034335

調(diào)用自定義的函數(shù)

import sys
sys.path.append(r"D:\python\customize") # 設(shè)置自定義的路徑
import greet                            # 調(diào)用自定義函數(shù)greet.py的文件名
greet.greet_user()                      # 調(diào)用函數(shù)方式

image-20211114002711631

參數(shù)的位置

函數(shù)調(diào)用要根據(jù)定義時(shí)參數(shù)變量的位置

def difference(x,y):
    diff = x - y
    print(diff)  # diff作為一個(gè)變量不用加雙引號(hào)颤陶，加了雙引號(hào)就會(huì)打印diff而不會(huì)打印計(jì)算的結(jié)果
    
difference(3,5)
difference(5,3)

image-20211115230334912

根據(jù)關(guān)鍵詞調(diào)用可不按照位置來(lái)

def difference(x,y):
    diff = x - y
    print(diff)
    
difference(y=3,x=5)

image-20211115230716208

默認(rèn)值

使用默認(rèn)值時(shí)臀栈，先列出沒(méi)有默認(rèn)值的參數(shù)娃圆。再列出有默認(rèn)值的參數(shù)

def difference(x,y=2):
    diff = x-y
    print(diff)
    
difference(5)
difference(5,3)

image-20211115231831534

參數(shù)可選

def difference(x,y,z=''):
    if z:                 # z 存在的時(shí)候
        diff = x-y+z
    else:
        diff = x+y
    print(diff)
    
difference(5,3)
difference(5,3,1)

image-20211117233949080

返回值

在函數(shù)中玫锋，可使用 return 語(yǔ)句將值返回到調(diào)用函數(shù)的代碼行。返回值讓你能夠?qū)⒊绦虻拇蟛糠址敝毓ぷ饕频胶瘮?shù)中去完成讼呢，從而簡(jiǎn)化主程序

def difference(x,y):
    diff = x-y
    return diff
    
z = difference(3,5)
print(z)

image-20211125170042675

函數(shù)與列表

傳遞列表

def greet_users(names):
    for name in names:
        msg = "Hello, " + name.title() + "!" # title返回"標(biāo)題化"的字符串,就是說(shuō)所有單詞都是以大寫(xiě)開(kāi)始撩鹿，其余字母均為小寫(xiě)
        print(msg)

usernames = ['hannah', 'ty', 'margot']
greet_users(usernames)

image-20211124130856413

修改列表

def print_objects(unprinted_objects, completed_objects):                 
    while unprinted_objects:                     # 當(dāng)unprinted_objects列表有值的時(shí)候執(zhí)行下列指令
        current = unprinted_objects.pop()        # 刪除unprinted_objects的最后一個(gè)元素并將該元素賦值給current
        print("Printing object: " + current)     #打印刪除的元素
        completed_objects.append(current)        # 在completed_objects列表末尾添加current
def show_completed(completed_objects):
    print("\nThe following objects have been printed:")
    for completed_object in completed_objects:
        print(completed_object)
        
unprinted_objects = ["A","b","C"]
completed_objects = []

print_objects(unprinted_objects, completed_objects)
show_completed(completed_objects)

image-20211124142415746

禁止修改列表

上述修改是在unprinted_objects列表里面直接刪除，執(zhí)行完函數(shù)之后悦屏，該列表沒(méi)有元素變?yōu)榭樟斜斫诼伲蚝瘮?shù)傳遞列表的副本可避免這個(gè)問(wèn)題。unprinted_objects[:]即為unprinted_objects的副本

調(diào)用上述函數(shù)時(shí)可以用

print_objects(unprinted_objects[:], completed_objects)

任意數(shù)量的實(shí)參

傳遞任意數(shù)量的實(shí)參

當(dāng)不知道函數(shù)需要傳遞多少個(gè)實(shí)參的時(shí)候础爬，可以用*加形參來(lái)表示

如下甫贯，*words表示創(chuàng)建一個(gè)名為words的空元組

def print_words(*words):
    print(words)
    
print_words('a')
print_words('apple','grape')

image-20211125144031631

結(jié)合使用位置實(shí)參和任意數(shù)量實(shí)參

def print_words(type,*examples):
    print('type: '+type)
    for example in examples:
        print(example)
        
print_words('n','noun','group')
print_words('v','ask','do','can')   

image-20211125145850915

使用任意數(shù)量的關(guān)鍵字實(shí)參

**加形參創(chuàng)建一個(gè)字典以使函數(shù)接受任意的鍵值對(duì)

def user_profile(name,nation,**user_info):
    profile = {}
    profile['name'] = name
    profile['nationality'] = nation
    for key,value in user_info.items():
        profile[key] = value
    return profile
    
user = user_profile('Jenny','America',gender='woman',age=25)
print(user)

image-20211125154628391

將函數(shù)存儲(chǔ)在模塊中

模塊是擴(kuò)展名為.py的文件，包含要導(dǎo)入到程序中的代碼看蚜。

在D:\python_test目錄下創(chuàng)建一個(gè)存放長(zhǎng)方形周長(zhǎng)和面積計(jì)算公式的py文件叫搁，內(nèi)容如下，記為rectangle_functions.py供炎，該文件即為一個(gè)模塊

def rectangle_C(a,b):
    c=(a+b)*2
    return c
    
def rectangle_S(a,b):
    s=a*b
    return s

導(dǎo)入整個(gè)模塊

在rectangle_functions.py所在的目錄中創(chuàng)建另一個(gè)名為rectangle.py的文件渴逻，內(nèi)容如下

import rectangle_functions

C=rectangle_functions.rectangle_C(4,5)
S=rectangle_functions.rectangle_S(4,5)
print('長(zhǎng)度為4，寬度為5的長(zhǎng)方形')
print('周長(zhǎng)為'+str(C)+'音诫，面積為'+str(S))

image-20211125164432732

調(diào)用rectangle

import sys
sys.path.append(r"D:\python_test") 
import rectangle                           

image-20211125171040461

# 導(dǎo)入特定的的函數(shù)
from rectangle_functions import rectangle_C

# 導(dǎo)入全部函數(shù)
from rectangle_functions import *

使用 as 指定別名

如果要導(dǎo)入的函數(shù)的名稱(chēng)可能與程序中現(xiàn)有的名稱(chēng)沖突裸卫，或者函數(shù)的名稱(chēng)太長(zhǎng)，可指定簡(jiǎn)短而獨(dú)一無(wú)二的別名

# 使用 as 給模塊指定別名
import rectangle_functions as rf
# 調(diào)用方式
C=rf.rectangle_C(4,5)

# 使用 as 給函數(shù)指定別名
from rectangle_functions import rectangle_C as c
# 調(diào)用方式
C=c(4,5)

參考書(shū)目：Python編程從入門(mén)到實(shí)踐 - Eric Matthes 著纽竣，袁國(guó)忠 譯