#if…
#if … else…
#if… elif…elif…else…
Light = ‘on’
if Light == ‘on’: print(‘open’) #使用雙等號,單等號是指定
if Light == ‘on’:
print(‘open’) #分兩行的話,第二行的前方要縮排
執行結果:
open
open
account = ‘abc123’
password = ‘abc123’
if account == password :
print(‘login’)
else: #else後面加:
print(‘error’)
if account == password : print(‘login’)
else: print(‘error’)
執行結果:
login
login
account = ‘abc123’
password = ‘abc123’
if account == ‘ ‘ : print(‘account is null’)
elif password == ‘ ‘ : print(‘password is null’)
#elif account != password : print(“account or password error”) #這段程式碼不知道為何錯誤
elif account != password : print(“account or password error”) #依照上一行,一模一樣打又正確
elif account == password : print (‘login’)
執行結果
login
account = ‘abc123’
password = ‘abc123a’
if account == ‘ ‘ : print(‘account is null’)
elif password == ‘ ‘ : print(‘password is null’)
elif account == password : print (‘login’)
#elif account != password : print(‘account or password error) #這段程式碼不知道為何錯誤
#Python invalid non-printable character U+00A0:
#由于习惯了复制现成的代码，导致报错，所以一般先处理下复制的代码，去掉空格，或者再不行用笨办法重新敲一遍
else : print(‘account or password error’)
執行結果:
account or password error
account = ‘abc123’
password = ‘abc123A’
if account == ‘ ‘ : print(‘account is null’)
elif password == ‘ ‘ : print(‘password is null’)
#elif account != password : print (“account or password error”) #這段程式碼不知道為何錯誤
elif account != password : print (‘account or password error’)
elif account == password : print (‘login’)
執行結果:
account or password error
print(“請輸入帳號”)
acc = input()
print(“請輸入密碼”)
pwd = input()
account = “abc123”
password = “ABC456”
if account == acc and password == pwd : print(“login”)
else : print(“account or password error”)
執行結果:
print(“請輸入帳號”)
acc = input()
print(“請輸入密碼”)
pwd = input()
account = “abc123”
password = “ABC456”
if account != acc or password != pwd : print(“account or password error”)
else : print(“login”)
執行結果同上
print(“請輸入您的體重”)
weight = float(input())
Goal =60 #目標體重
Health = 50 #理想體重
if weight <= Goal:
if weight <= Health: print(“恭喜您達到理想體重”)
else: print(“恭喜您達到目標體重”) #跟上面的if同縮排
else: print(“請繼續努力”) #else後面要加:
#槽狀IF
print(“恭喜您達到理想體重”) if weight <= Health else print(“恭喜您達到理想體重”) if weight <= Goal else print(“請繼續努力”)
#寫成一行,不可分行,不用:(冒號),一行式邏輯比較容易理解
執行結果同上