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Language elements
Instructions and procedures
The hardware system of a computer usually consists of five parts ： Arithmetic unit 、 controller 、 Memory 、 Input devices and output devices .
Combination of arithmetic unit and controller ： a central processor . Execute various operations and control instructions and process data in computer software .
Combination of instructions ： Program .
Common data types
- plastic ：python Can handle integer of any size （python 3 There are only int This kind of ）
- floating-point ： Floating point numbers are decimals
- String type ： Any text enclosed in single or double quotation marks .'hello' and "hello"
- Boolean type ： Only True and False Two kinds of
Variable naming
- Variable names are made up of letters 、 Numbers and underscores make up , The number can't start
- Case sensitive （ Case indicates different variables ）
- Don't conflict with keywords and system reserved words
Use of variables
python Can be used in
type Function to check the category of variables .
a=100
print(type(a)) # <class 'int'>
have access to python The built-in functions in convert variable types .
int()： Will a 【 Value or string 】 convert to 【 Integers 】
float()： Will a 【 character string 】 convert to 【 Floating point numbers 】
str()： take 【 Specified objects 】 convert to 【 character string 】
chr()： take 【 Integers 】 convert to 【 The string corresponding to this encoding （ A character ）】
ord()： take 【 character string （ A character ）】 convert to 【 Corresponding code （ Integers ）】
chr() and ord() Reverse each other .a=1
b=2
print('%d + %d = %d' % (a,b,a+b)) #1 + 2 = 3
%d Placeholder for integers ,
%f Placeholder for decimal , After the string
% The following variable value will replace the placeholder and output to the terminal .
Operator
- Arithmetic operator ：
**%///*-+
- Assignment operator ：
= += -= *= /= //=
- Comparison operator ：
> < >= <= == !=
- Logical operators ：
and or not
- An operator ：
& | ~ ^ >> <<
Operator priority ： Monocular operator （
~ + -）> Arithmetic operator > An operator > Comparison operator . With parentheses , Parentheses take precedence .
Branching structure
One statement is executed in sequence ： Sequential structure Branching structure （ Selection structure ）
python Keywords for constructing branch structures in ：
if 、
else 、
elif'''
Judge whether the input side length can form a triangle , If you can, calculate the perimeter and area of the triangle
Author:AXYZdong
'''
a = float(input('a = '))
b = float(input('b = '))
c = float(input('c = '))
if a+b > c and a +c > b and b+c >a :
print(' Perimeter = %f' % (a+b+c))
p = (a+b+c)/2
area = (p*(p-a)*(p-b)*(p-c))**0.5
print(' area = %f' % (area))
else:
print(' Can't make a triangle ')
Loop structure
for-in loop
Be clear about Number of loop executions perhaps To iterate over a container , Recommended
for-in loop .
example ： Calculation 1~100 The result of the summation
'''
1~100 Sum up
Author:AXYZdong
'''
sum = 0
for x in range(101): # for x in range(1,101):
sum = sum + x
print(sum)
range(101)： produce 0~100 Range of integers , Can't get 101.
range(1,101)： produce 1~100 Range of integers , amount to [1,101)
range(1,101,2)： produce 1~100 Odd numbers in the range , among 2 It's the step length , Each increment
range(100,0,-2)： produce 100~1 Even numbers in the range , among -2 It's the step length , Decrease each time
1~100 Sum even numbers in the range ？'''
use for Cycle to achieve 1~100 Sum even numbers in the range
Author:AXYZdong
'''
sum = 0
for x in range(2,101,2): # for x in range(100,0,-2):
sum = sum + x
print(sum)
range(2,101,2)： from 2 Start with each 2 The step size is incremented , produce 2~100 The scope of the （ They are all even numbers ）
while loop
Do not know the cycle structure of specific cycle times , Recommended
while loop .while The ability to produce or convert out of
bool Value to control the loop , The value of the expression is
True Then continue the cycle ; Expression for
False End cycle .
'''
Guess the number game
Author:AXYZdong
'''
import random
ans = random.randint (1,10)
counter = 0
while True:
counter += 1
num = int(input(' Please enter ：'))
if num > ans:
print(' A little bigger ')
elif num < ans:
print(' Smaller one ')
else:
print(' Congratulations on your guesses ')
break
print(' You guessed it all together %d Time '% (counter))
if counter > 5:
print(' Your luck is too bad ')
random.randint( Parameters 1, Parameters 2)- Parameters 1、 Parameters 2 It has to be an integer
- The return value of the function is the parameter 1 And parameters 2 Any number between , Closed interval [ Parameters 1, Parameters 2]（python 3 Verified in the environment ）
example ： Enter two positive integers , Calculate their greatest common divisor and least common multiple .
The greatest common factor ： The largest number in the common factor of the two numbers Minimum common multiple ： The product of two natural numbers divided by their greatest common factor '''
Enter two positive integers , Find their greatest common divisor and least common multiple
Author:AXYZdong
'''
x = int(input('x = '))
y = int(input('y = '))
if x > y:
x,y = y,x
for common in range(x,0,-1):
if x%common == 0 and y%common == 0:
print('%d and %d The greatest common divisor is %d' % (x,y,common))
print('%d and %d The minimum common multiple is %d' % (x,y,(x*y//common)) ) # The product of two natural numbers is equal to the greatest common factor of these two numbers multiplied by their least common multiple
break
reference
[1]：https://github.com/jackfrued/Python-100-Days[2]：Python Programming fast : Automate tedious work / ( beautiful ) Svegart (A1 Sweigart) Writing ; Translated by Wang Haipeng . Beijing : People's post and Telecommunications Press ,2016.7[3]：Python Chinese guide ; author ： Wang Bingming , edition ：v1.0
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