Python tutorial #4 : arithmetic operations

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Arithmetic operations cheat sheet

x + y    addition 
x - y    subtraction
x * y    multiplication
x / y    division
x // y   Division (rounded down to the nearest whole number)
x % y    Surplus 
-x       Sign inversion
+x       As it is 
x ** y   Exponentiation

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python arithmetic operations priority

↑ High priority

(), [], {},             list / tuple / dict
await x                 Await
**                      Exponentiation
+x, -x, ~x              Positive / Negative / Bitwise
*, @, /, //, %          Multiplication / matrix multiplication / division / truncation division / remainder
+, -                    Addition and subtraction
<<, >>                  Shift operation
&                       Bitwise AND
^                       Bitwise XOR
|                       Bitwise OR
in, not in, is, is not, Comparison including affiliation and identity tests
<, <=, >, >=, !=, ==    Comparison including affiliation and identity tests
not x                   Boolean operation NOT
and                     Boolean operation AND
or                      Boolean operation OR
if -- else              Conditional expression
lambda                  Lambda expression

↓ Low priority

1 + 2 * 3 = 7

1 + 3 / 7 = 0.4285714285714286

1 + 8 // 2 = 5

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Addition Addition + Operator

1 + 2 = 3

1.23 + 2.6 = 3.83

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Subtraction -Operator

Unable to do subtraction in python

2 - 5 = -3

This is the code 2 + -5, so if you want to do a subtraction, you have to write it at the end of the column.

1 - 6 / 2 = -2.0

error

6 / 2 - 1 = 2.0

correct

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Multiplication *operator

2 * 3 = 6

6.5 * 20.5 = 133.25

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Division /Operator

6 / 2 = 3.0

3 / 7 = 0.42857142857142855

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25 / 4 = 6.25

Handling of decimal point

3 / 7 = 0.42857142857142855

Output in python

0.428571428571428571

Original answer

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3 / 11 = 0.2727272727272727

Output in python

0.27272727272727272

Original answer

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Division displays 17 digits after the decimal point. Numbers longer than 17 digits are not displayed even if they exist

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arithmetic operations Rounding

1 / 9 = 0.1111111111111111
2 / 9 = 0.2222222222222222
3 / 9 = 0.3333333333333333
4 / 9 = 0.4444444444444444
5 / 9 = 0.5555555555555556
6 / 9 = 0.6666666666666666
7 / 9 = 0.7777777777777778
8 / 9 = 0.8888888888888888
9 / 9 = 1.0

・For some reason, indivisible numbers between 5 and 7 are rounded up to the nearest whole number.
・Indivisible numbers in 0.999 ... are displayed as approximately 1.0

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Integer part of division Integer division //Operator omitted

Truncate

When performing division, it is recommended to use //, which is rounded down to the nearest whole number, unless accurate calculation is required.

Reason

・Numbers (ints) that have a decimal point are called float types, which complicates the code. ・Execution speed takes about 10 times (slows down) ・Increased probability of human error

25 // 4 = 6

Handling of decimal points in //

1 // 9 = 0
2 // 9 = 0
3 // 9 = 0
4 // 9 = 0
5 // 9 = 0
6 // 9 = 0
7 // 9 = 0
8 // 9 = 0
9 // 9 = 1

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Division remainder remainder mod %operator Percentage

% Is often used mainly when using machine learning. Let's take the gross profit amount and the gross profit rate as an example.

・Cost
cost = 14

・Selling price
sales = 85

・Gross profit
gp = (sales - cost)

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print('{:,}'.format(gp))

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71

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・Gross profit margin
gpr = gp / sales

print('{:%}'.format(gpr))

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83.529412%

You can see that the gross margin is about 83%

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Exponentiation **Operator

4 ** 4 = 4 * 4 * 4 * 4 = 256

5 ** 3 = 5 * 5 * 5 = 125

Cubic centimeters Useful when calculating square centimeters