>, <, ==( And so on ), !=( It's not equal to ), >=, <=
notes ：python The comparison size in is the comparison size between data of the same type
-------> Comparing sizes yields Boolean values
print(3 > 4) expand — ask ： Why? python Ability to compare sizes ？
python The code value used is called the universal code ：unicode, It is ASCII Expansion of coding
A-Z Corresponding decimal code ：65-90
a-z Corresponding coding value :97-122
print('A' < 'a')print(0 != 1)print(0 == 1)>= 、 <=
print(2 >= 2) Example ：
Determine if the year is a leap year ：
year = 2004result = (year % 4 ==0 and year % 100 != 0) or (year % 400 == 0)print(result)=, += ,-= , =, /=, //=, %=,
Count the right side of the equal sign first , Assign a value to the left of the equal sign
a = 10a += 5# a = a + 5a **= 2# a = a ** 2print(a)a %= 2# a = a % 2print(a)# Compound assignment operator a *= a + 3# a = a*(a+3)print(a) Operator priority
a. First calculate the parentheses as a whole
b. Arithmetic operator ：* * > *,/,//,% > +,-
c. Arithmetic operator > Comparison operator > Logical operators > Assignment operator
practice ：
1、 The conversion between Fahrenheit and temperature ：C = (F - 32)/1.8
C = 36F = round(C * 1.8 + 32, 2)print(f' Centigrade {C} Equal to degrees Fahrenheit {F}')F = 109C = round((F - 32) / 1.8, 2)print(f' Fahrenheit {C} Equal to centigrade {F}') Add ：
round( Parameters 1, Parameters 2)----> Parameters 1 Equal to the value , Parameter 2: the number of decimal places to be reserved
2、 According to the specified radius of the circle , Calculate the circumference and area of a circle .
import mathr = 3c = round(2 * r * math.pi, 2)s = round(r ** 2 * math.pi, 2)print(f' The circumference of the circle is ：{c}')print(f' The area of the circle is ：{s}')----- Numbers 、 Boolean data type conversion
All data can be converted to Boolean values （bool）
# bool()print(bool(0), bool(1), bool(-1))print(bool(''), bool([]), bool({}), bool(None)) # An empty string 、 An empty list 、 An empty dictionary 、 Null value notes ：
a.0 Convert to False, Not 0 Is full of Ture
b. All null objects are False
a. Boolean values can be converted to integers , Can only turn 0 and 1：False—0,Ture—1
print(int(bool(100)))b. floating-point (float) Can be converted to an integer ： Round to the small
print(int(0.515646))#---->0print(int(.1))#---->0print(int(1.))#---->1print(int(9.64631653))#---->9c. character string （ A string that is an integer without quotation marks ） Can be converted to an integer
print(int(input(' Please enter an integer ：')))print(int('156486'))a. Integer to floating point
print(float(1))b. Strings that are numbers without quotation marks can be converted to floating-point type
print(float('.9'))#--->0.9c. Boolean values can be converted to floating point type :False—>0.0;Ture—>1.0
print(float(False))notes ：bool() int() float() list() etc. ----> Constructor Syntax
Branch structure keywords ：if、else、elif、
Single branch structure grammar ：
if Conditions :
Code segment 1
else:
Code segment 2
Case study ： Account password login
username = input(' Please enter a user name ：')password = input(' Please input a password ：')if username == 'admin' and password == '123456': print(' Landing successful ')else: print(' Login failed ') notes : Indent ： Generally think of indentation as four spaces , The indentation of a program must be consistent
practice ： Judge whether a year is a leap year ？
year = int(input(' Please enter a year ：'))if (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0): print(f'{year} Year is a leap year ')else: print(f'{year} Year is a normal year ') Multi branch structure grammar ：
if Conditions :
Code segment 1
elif Conditions 2:
Code segment 2
…
else:
Code segment n
practice ： Judge whether a year is a leap year ？
year = int(input(' Please enter a year ：'))if year % 4 == 0 and year % 100 != 0: print(f'{year} Year is a leap year ')elif year % 400 == 0: print(f'{year} Year is a leap year ')else: print(f'{year} Year is a normal year ') example ： Judging whether a person is an adult
Common writing ：
age = int(input(' Please enter age ：'))if age < 18: print(' A minor ')else: print(' adult ') Ternary operator syntax ：
Variable = ‘ result 1’ Conditions else ‘ result 2’
Conditions established , Result is result 1, The opposite is the result 2
Improved writing ：
result = ' adult ' if age >= 18 else ' A minor 'print(result)a = float(input(' Please input the side length a:'))b = float(input(' Please input the side length b:'))c = float(input(' Please input the side length c:'))C = a + b + c # Perimeter s = 0.5*CS = (s*(s-a)*(s-b)*(s-c))**0.5# Helen's formula ：（ Half the circumference of a triangle ）*（ Half the circumference of a triangle -a）*（ Half the circumference of a triangle -b）*（ Half the circumference of a triangle -c）**0.5if a + b > c and a + c > b and b + c > a: print(" Can form triangles ") print(f' The perimeter of the triangle is {round(C,2)}, Area is {round(S,2)}.')# round() Keep the decimal places else: print(' Can't make a triangle ') requirement ： If the score entered is in 90 More than （ contain 90 branch ） Output A;80 branch -90 branch （ Not included 90 branch ） Output B;
70 branch -80 branch （ Not included 80 branch ） Output C;60 branch -70 branch （ Not included 70 branch ） Output D;60 The output is as follows E.
score = int(input(' Please enter the grade to be converted ：'))if score >= 90: print(' This grade is ：A')elif score >= 80: print(' This grade is ：B')elif score >= 70: print(' This grade is ：C')elif score >= 60: print(' This grade is ：D')else: print(' This grade is ：E')num = float(input(' Please input the data to be converted :'))unit = input(' Please enter the unit to be converted :')if unit == 'in' or unit == ' feet ': num1 = num * 2.54 print(f'{num} centimeter ={num1} feet ')elif unit == 'cm' or unit == ' centimeter ': num2 = num / 2.54 print(f'{num} feet ={num2} centimeter ')else: print(' Please enter the correct unit ')author ： Have a strong sense of self-management .
Game programming , A game development favorite ~
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