格式化输出，基本运算符与if判断

格式化输出

a = 'Tom'
b = 'is'
c = 'a'
d = 'good'
e = 'boy'

print(a + b)

Tomis

print(a, b, c, d, e)
print(a + ' ' + b + '' + c)

Tom is a good boy
Tom isa

%占位符（了解）

print('%s %s %s %s %s' % (a, b, c, d, e))

Tom is a good boy

print('%s %s %s %s' % (a, b, c, d, e))

---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-4-07e6d91630cb> in <module>
----> 1 print('%s %s %s %s' % (a, b, c, d, e))

TypeError: not all arguments converted during string formatting

print('%s %s %s' % (a, b,))

---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-12-b0716021e3eb> in <module>
----> 1 print('%s %s %s' % (a, b,))

TypeError: not enough arguments for format string

需要几个就传几个

format占位符（了解）

print('{} {} {} '.format(a, b, c))

Tom is a 

print('{:.2f}'.format(15.3231))

15.32

f-string格式化（推荐使用）

print(f'{a} {b} {c} {d} {e}')

Tom is a good boy

print(F'{a} {b} {c} : {d} {e}')

Tom is a : good boy

salary = 15000.6842
print(f'{salary:.3f}')

15000.684

name = 'Tom'
height = 185
weight = 150

print('name:%s height:%s weight:%s' % (name, height, weight))
print('name:{} height:{} weight:{}'.format(name, height, weight))
print(f'name:{name} height:{height} weight:{weight}')

name:Tom height:185 weight:150
name:Tom height:185 weight:150
name:Tom height:185 weight:150

基本运算符

• 算数运算符(掌握)
• 比较运算符（熟悉）
• 赋值运算符（掌握）
• 逻辑运算符（掌握）
• 身份运算符（掌握）

算数运算符

a = 10 b = 20

+	加	a+b=30
-	减	a-b=-10
*	乘	a*b=200
/	除	a/b=0.5
**	幂	a**b = 10^20^
//	整除	a//b =0
%	取模	a%b=10

x = 1
y = 2

print(x + y)
print(x - y)
print(x * y)
print(x / y)
print(x ** y)  # 幂
print(x // y)  # 整除
print(x % y)  # 取余

3
-1
2
0.5
1
0
1

比较运算符

a = 10 b = 20

运算符	描述	实例
==	等于	(a==b) 返回False
！=	不等于	(a!=b) 返回True
>	大于	(a>b)返回False
<	小于	(a<b)返回True
>=	大于等于	(a>=b)返回False
<=	小于等于	(a<=b)返回True

x = 100
print(x == 100)
print(x != 100)
print(x > 90)
print(x < 90)
print(x >= 90)
print(x <= 90)
type(x < 120)

True
False
True
False
True
False

bool

赋值运算符

a = 10 b = 20

运算符	描述	实例
=	赋值	c=a+b即a+b的结果赋值给c
+=	加法赋值	c+=a即c=c+a
-=	减法赋值	c-=a即c=c-a
*=	乘法赋值	c=a 即c=c a
/=	除法赋值	c/=a即c=c/a
**=	幂赋值	c** a=a 即c=c **a
//=	取整除赋值	c//a = a即c=c//a
%=	取模赋值	c%a=a 即c=c%a

y = 500
print(y)
id(y)

500

1638542637552

y += 100
print(y)
id(y)

600

1638542637616

y -= 100
print(y)
id(y)

500

1638542637584

y *= 10
print(y)
id(y)

5000

1638542638832

y /= 100
print(y)
id(y)

50.0

1638541796312

逻辑运算符

a = 10 b = 20

运算符	描述	实例
and	布尔“与”-如果a为False，则返回False，否则返回b的计算值	(a andb)返回20
or	布尔“或”-如果a为非0，则返回a,否则返回b的计算值	(a or b)返回 10
not	布尔“非”-如果a为True，则返回False	not(a and b)返回False

1 > 2 and 4 > 3

False

1 > 2 or 4 > 3

True

not 1 > 2 and 4 > 3

True

身份运算符（纯了解）

x = 257
y = 257

print(id(x) == id(y))

False

print(x is y)

False

补充

• python运算符优先级（掌握）
• 链式赋值（掌握）
• 交叉赋值（掌握）
• 解压缩（掌握）

链式运算符

x = 10
y = 10
z = 10
print(x, y, z)

10 10 10

x = y = z = 10
print(x, y, z)

10 10 10

交叉运算符

x = 10
y = 20

z = x
x = y
y = z
print(x, y)

20 10

x = 10
y = 20

x, y = y, x
print(x, y)

20 10

解压缩

tom_hobbies_list = ['fishing', 'reading', 'running']
other_hobbies_list = ['sleeping', 'eating', 'drinking', 'playing']

hobby1 = tom_hobbies_list[2]
hobby2 = tom_hobbies_list[0]

print(hobby1, hobby2)

running fishing

hobby1, hobby2, hobby3 = tom_hobbies_list
print(hobby1, hobby2, hobby3)

fishing reading running

hobby1, hobby2 = tom_hobbies_list
print(hobby1, hobby2)

---------------------------------------------------------------------------

ValueError                                Traceback (most recent call last)

<ipython-input-37-9ca5877dad71> in <module>
----> 1 hobby1, hobby2 = tom_hobbies_list
      2 print(hobby1, hobby2)

ValueError: too many values to unpack (expected 2)

hobby1, hobby2, hobby3 = tom_hobbies_list
print(hobby1, hobby2)

fishing reading

hobby1, _, hobby3, _ = other_hobbies_list
print(hobby1, hobby3)

sleeping drinking

hobby1, hobby2, *_ = other_hobbies_list
print(hobby1, hobby2)

sleeping eating

if判断

if ...

if 条件 :
    代码块

dog1 = '疯狗'
dog2 = '正常狗'

if dog1 == '疯狗' :
    print('远离它')

远离它

if...else...

if 条件 :
    代码块
else :
    代码块
    

if dog1 == '疯狗' :
    print('远离它')
else :
    print('抚摸它')

远离它

if...elif...else..

if 条件:
    代码块
elif 条件:
    代码块
else  :
    代码块

# 180以上全票，140-170半票，120以下免票

height = int(input('>>>请输入您的身高：'))

if height > 180 :
    print('全票')
elif height < 120 :
    print('免票')
elif height <170 and height > 140 :
    print('半票')
else :
    print('身高不符')

>>>请输入您的身高：185
全票

if 嵌套

if 条件 :
代码
else :
if 条件 :
代码
else :
代码

while True :
    age = int(input('>>>请输入年龄：'))
    if age < 50 :
        print('too small')
    elif age > 50 :
        print('too big')
    else :
        print('congratulations')
        break

>>>请输入年龄：39
too small
>>>请输入年龄：59
too big
>>>请输入年龄：50
congratulations