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Python Full Stack Road Series: Assignment and Operators

高洛峰
Release: 2017-02-09 11:02:06
Original
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Before continuing with the following article, let's first take a look at several operators provided by Python for us. Define two variables, a and b. The value of a is 10 and the value of b is 20.

Arithmetic Operator

##*Multiple, the two numbers are equivalent or Returns a string repeated several timesa*b=200/Divide two objectsb/a=2%Take the membrane and return the remainder of the divisionb%a=0**Power, returns the y power of xa**b=100000000000000000000L//Remainder of integer division, return the integer part of the quotienta//b=0##Comparison operator
Operator Description Example
+ Add, add two objects a+b=30
- Subtract, subtract two objects, you may get a negative number a-b=-10

Operator##====Equals , compare whether two objects are equala==bReturn False!=Not equal, compare whether two objects are not equala!=b returns TrueNot equal, compare whether two objects are equal is greater than, compares whether x is greater than y, Less than, compare whether x is less than y##>=Greater than or equal to, compare whether x is greater than or equal to ya>=b returns False<=Less than or equal to, compare Whether x is less than or equal to ya<=b returns True
Description Instance
##<>
a< ;>b returns True >
a>b returns False <
a
Assignment operator
## Operator

DescriptionInstanceAssignment Operator c=a+b, assign the operation result of a+b to c##+=addition copy operatorc += a, etc. Effective for c = c + a-=Subtractive copy operatorc -= a is equivalent to c = c - a*=Multiplicative copy operatorc = a is equivalent to c = c a/=c /= a is equivalent to c = c / a%=Modulo assignment operatorc %= a is equivalent to c = c % a**=Power assignment operator c = a is equivalent to c = c a//=c //= a is equivalent to c = c // aOperation Symbol
=
Division copy operator
Integer division assignment operator
Logical operator

Description

Instanceand"with"a and b returns trueor"or"a or b returns truenot "Not"no(a and b) returns false##Member operatorOperator
Description

not in

赋值语句的语法

inReturns True if the value is found in the specified sequence , otherwise it returns False
If the value is not found in the specified sequence, it returns True, otherwise it returns false
运算解释
spam='Spam'基本形式
spam, ham='yum', 'YUM'元组赋值运算
[spam, han]=['yum', 'YUM']列表赋值运算
a,b,c,d='spam'序列赋值运算,通用性
a, *b='spam'扩展的序列解包
spam = ham = 'hello'多目标赋值运算
spams += 42增强赋值运算

实例

序列运算

>>> nudge = 1
>>> wink = 2
>>> A, B = nudge, wink
>>> A,B
(1, 2)
# 嵌套的方式
>>> ((a, b), c) = ('SP', 'AM')
>>> a, b, c
('S', 'P', 'AM')<p>扩展的序列解包</p>
<p>一个列表赋给了带星号的名称,该列表收集了序列中没有赋值给其他名称的所有项。</p>
<p>先定义一个seq序列用于测试:</p>
<pre class="brush:php;toolbar:false">>>> seq = [1, 2, 3, 4]
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a匹配序列中的第一项,b匹配剩下的内容

>>> a, *b = seq
>>> a, b
(1, [2, 3, 4])
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b匹配序列中的最后一项,a匹配序列中最后一项之前的所有内容

>>> *a, b = seq
>>> a,b
([1, 2, 3], 4)
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第一项个最后一项分别赋值给了ac,而b获取了二者之间的所有内容。

>>> *a, b, c = seq
>>> a,b,c
([1, 2], 3, 4)
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带星号的名称可能只匹配单个的项,但是,总会向其复制一个列表,如果没有剩下的内容可以匹配那么会返回一个空列表:

>>> a,b,c,*d = seq
>>> print(a,b,c,d)
1 2 3 [4]
>>> a,b,c,d,*e = seq
>>> print(a,b,c,d,e)
1 2 3 4 []
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多目标赋值语句就是直接把所有提供的变量名都赋值给右侧的对象

>>> a = b = c = 'As'
>>> a,b,c
('As', 'As', 'As')
# 所引用的值也都是同一个
>>> id(a),id(b),id(c)
(4331109208, 4331109208, 4331109208)
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Before continuing with the following article, let's first take a look at several operators provided by Python for us. Define two variables, a and b. The value of a is 10 and the value of b is 20.

Arithmetic Operator

##*Multiple, the two numbers are equivalent or Returns a string repeated several timesa*b=200/Divide two objectsb/a=2%Take the membrane and return the remainder of the divisionb%a=0**Power, returns the y power of xa**b=100000000000000000000L//Remainder of integer division, return the integer part of the quotienta//b=0##Comparison operator
Operator Description Example
+ Add, add two objects a+b=30
- Subtract, subtract two objects, you may get a negative number a-b=-10

Operator##====Equals , compare whether two objects are equala==bReturn False!=Not equal, compare whether two objects are not equala!=b returns TrueNot equal, compare whether two objects are equal is greater than, compares whether x is greater than y, Less than, compare whether x is less than y##>=Greater than or equal to, compare whether x is greater than or equal to ya>=b returns False<=Less than or equal to, compare Whether x is less than or equal to ya<=b returns True
Description Instance
##<>
a< ;>b returns True >
a>b returns False <
a
Assignment operator
## Operator

DescriptionInstanceAssignment Operator c=a+b, assign the operation result of a+b to c##+=addition copy operatorc += a, etc. Effective for c = c + a-=Subtractive copy operatorc -= a is equivalent to c = c - a*=Multiplicative copy operatorc = a is equivalent to c = c a/=c /= a is equivalent to c = c / a%=Modulo assignment operatorc %= a is equivalent to c = c % a**=Power assignment operator c = a is equivalent to c = c a//=c //= a is equivalent to c = c // aOperation Symbol
=
Division copy operator
Integer division assignment operator
Logical operator

Description

Instanceand"with"a and b returns trueor"or"a or b returns truenot "Not"no(a and b) returns false##Member operatorOperator
Description

not in

赋值语句的语法

inReturns True if the value is found in the specified sequence , otherwise it returns False
If the value is not found in the specified sequence, it returns True, otherwise it returns false
运算解释
spam='Spam'基本形式
spam, ham='yum', 'YUM'元组赋值运算
[spam, han]=['yum', 'YUM']列表赋值运算
a,b,c,d='spam'序列赋值运算,通用性
a, *b='spam'扩展的序列解包
spam = ham = 'hello'多目标赋值运算
spams += 42增强赋值运算

实例

序列运算

>>> nudge = 1
>>> wink = 2
>>> A, B = nudge, wink
>>> A,B
(1, 2)
# 嵌套的方式
>>> ((a, b), c) = ('SP', 'AM')
>>> a, b, c
('S', 'P', 'AM')<p>扩展的序列解包</p>
<p>一个列表赋给了带星号的名称,该列表收集了序列中没有赋值给其他名称的所有项。</p>
<p>先定义一个seq序列用于测试:</p>
<pre class="brush:php;toolbar:false">>>> seq = [1, 2, 3, 4]
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a匹配序列中的第一项,b匹配剩下的内容

>>> a, *b = seq
>>> a, b
(1, [2, 3, 4])
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b匹配序列中的最后一项,a匹配序列中最后一项之前的所有内容

>>> *a, b = seq
>>> a,b
([1, 2, 3], 4)
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第一项个最后一项分别赋值给了ac,而b获取了二者之间的所有内容。

>>> *a, b, c = seq
>>> a,b,c
([1, 2], 3, 4)
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Copy after login

带星号的名称可能只匹配单个的项,但是,总会向其复制一个列表,如果没有剩下的内容可以匹配那么会返回一个空列表:

>>> a,b,c,*d = seq
>>> print(a,b,c,d)
1 2 3 [4]
>>> a,b,c,d,*e = seq
>>> print(a,b,c,d,e)
1 2 3 4 []
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多目标赋值语句就是直接把所有提供的变量名都赋值给右侧的对象

>>> a = b = c = 'As'
>>> a,b,c
('As', 'As', 'As')
# 所引用的值也都是同一个
>>> id(a),id(b),id(c)
(4331109208, 4331109208, 4331109208)
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