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How IOS developers learn python programming 2-operator 1

2022-01-31 04:48:58 Sissy's father

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Python The language supports the following types of operators :

  1. Arithmetic operator
  2. Compare ( Relationship ) Operator
  3. Assignment operator
  4. Logical operators
  5. An operator
  6. member operator
  7. Identity operator
  8. Ternary operator

Arithmetic element operator

Python Medium Arithmetic element operator It's different from what we usually use OC perhaps Swift Is basically the same as , What's more special is :

  • **: power , return x Of y The next power . for example :10**20, Express 10 Of 20 Power .
  • //: Divide and conquer , Returns the integer part of the quotient . for example 9/2 Output 4.

What should be paid attention to during normal use :

  1.  / The result is a floating point number , Even if both numbers are integers , The result is also a floating-point number : 
>>> 9/3     
3.0

>>> 10/3
3.3333333333333335
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  1.  // Divide and conquer , Only integer part , The remainder is discarded : 
>>> 10//3   
3

>>> -10//3
-4  #  Rounding down 
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  1.  % Remainder operation  
>>> 10%3	 
1

>>> -10%3
2	#  Rounding down 
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  1.  divmod() Get quotient and remainder at the same time , The return value is tuple (x//y, x%y)
>>> divmod(10,3)	
(3,1)
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️ Be careful : Because of the precision of floating point numbers ,Python There are also some small computational problems :

0.1+0.1+0.1-0.3
5.551115123125783e-17
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have access to decimal modular :

from decimal import Decimal
Decimal('0.1')+Decimal('0.1')+Decimal('0.1')-Decimal('0.3')
Decimal('0.0')
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Comparison operator

Python Medium Comparison operator It's different from what we usually use OC perhaps Swift Is basically the same as , What's more special is :

  • <>: It's not equal to , Compare whether two objects don't want to wait , similar !=.(python3 in <> Have been abandoned )

What to pay attention to :

  1.  == Compare values (int And str You can't directly compare ): 
>>> a = 1
>>> b = 2
>>> a != b
True
>>> a <> b
  File "<stdin>", line 1
    a <> b
       ^
SyntaxError: invalid syntax
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  1. There is a comparison between strings ASCII value : 
>>> 'abc' < 'xyz'   # 97 98 99 < 120 121 122
True

>>> (3,2) < ('a','b')	
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '<' not supported between instances of 'int' and 'str'
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  1. Continuous comparison : 
>>> 3 > 2 > 1	# 3 > 2 and 2 > 1
True
>>> 3 > 2 > 2	# 3 > 2 and 2 > 2
False
>>> (3 > 2) > 1	# True and True > 1
False
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Assignment operator

Operator explain Example
= assignment x = y
-= Assignment reduction x -= y, x = x - y
*= Take the assignment x *= y, x = x * y
/= In addition to the assignment x /= y, x = x / y
%= Take the remainder and assign x %= y, x = x % y
**= Power assignment x **= y, x = x ** y
//= Take an integer and assign a value x //= y, x = x // y
&= Bitwise and assignment x &= y, x = x & y
= By bit or by assignment
^= Assign values by bitwise exclusive or x ^= y, x = x ^ y
<<= Shift left assignment x <<= y, x = x << y
>>= Shift assignment right x >>= y, x = x >> y

What to pay attention to :

  1.  python I won't support it a++ grammar : 
>>> a++ 		# python I won't support it a++ grammar 
  File "<stdin>", line 1
    a++
      ^
SyntaxError: invalid syntax
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  1.  += Can't open write + =: 
>>> a + = 1		#  Can't open write  + =
  File "<stdin>", line 1
    a + = 1
        ^
SyntaxError: invalid syntax
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An operator

Python Medium Arithmetic element operator It's different from what we usually use OC perhaps Swift Is basically the same as .

Logical operators

Python Support for logical operators , But not supported && and ||, Instead, more humanized English words and or not( It's all lowercase ):

  • a and b  Both are True The result is True
  • a or b  One of the two is True The result is True

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