Code block (start with colon and divide the same code block with indentation. This whole is code block)

Scope: scope of scope

if 10 == 11:
    print(1)
    print(2)
    print(3)
print(4)

#Indent: either all use / t Tab, or all use 4 spaces to express the same scope, which cannot be mixed together;

if 10 == 10:
    print(1)
    print(2)

Writing in other languages (understand)

if(10 == 10){
    print(1)
                    print(2)
                                                                                                    print(3)
}                                                        

Process control

Process: the process of code execution

Control: control during code execution

Three structures:

(1) Sequential structure: the default code is executed from top to bottom

(2) Branch structure: single branch, bidirectional branch, multiple branches, nested branch

(3) Loop structure: while / for

Single branch

if conditional expression:

　　code1

　　code2

When the conditional expression holds, it returns True and executes the corresponding code block

zhiye = "programmer"
if zhiye == "programmer":
    print("Get a high salary")
    print("More money,Few words,Die early")
    print("The amount of hair is becoming scarce")

Bidirectional branch (one out of two)

if conditional expression:

　　code1  ...

else:

　　code2...

If the conditional expression holds, it returns True and executes the code block of the if interval

If the conditional expression does not hold, return False and execute the code block of else interval

The code of if # branch is fast, which is also called town interval

The code block of else branch is also called false interval

zhiye = "Meituan takeout rider"
zhiye = "lawyer"
if zhiye == "Meituan takeout rider":
    print("Hit him")
    print("Scold him")
    print("Feed him chili water")
else:
    print("Give you a red flower")

input waits for the user to enter a string (Note: the result must be a string)

name = input("Hello~ What's your mother's name")
print(name,type(name))

Simulated website login

If admin = Sam, password: password = 111, login success will be displayed; otherwise, login failure will be displayed

admin = input("Please enter your account number:")
password = input("Please enter your password:")
if admin == "Sam" and password == "111":
    promt("Login successful")
else: 
    print("Login failed")

Multiple branches (one out of many)

"""

if conditional expression 1:

　　code1

elif conditional expression 2:

　　code2

elif conditional expression 3:

　　code3

else:

　　code4

If the conditional expression 1 is true, execute the corresponding branch code1, otherwise judge whether the conditional expression 2 is true

If conditional expression 2 is true, execute the corresponding branch code2, otherwise judge whether conditional expression 3 is true

If the conditional expression 3 is true, execute the corresponding branch code3. If it is not true, directly go to the ekse branch and the program is completed

elif can be 0 or more

else can be 0 or one

"""

youqian = False
youfang = False
youche = False
if youqian == True:
    print("It shows that this person is very powerful")
elif youfang == True:
    print("Can you make friends")
elif youche == True:
    print("Drove the Yadi Emma transfer car,Let's touch it")    
else:
    print("You'd better be a meituan rider")

print("<=======================>")

Nested branch

"" "single branch, two-way branch, nested combination of multiple branches" ""

youqian = True
youfang = True
youche = True
youyanzhi = True
youtili = False

if youqian == True:
    if youfang == True:
        if youche == True:
            if youyanzhi == True:
                if youtili == True:
                    print("I want to marry you~")
                else:
                    print("You go eat some big kidney and come back~")
            else:    
                print("You go to Thailand+the republic of korea,Plastic surgery")
else:
    print("You're a good man~")

Little practice

#height
#Girls looking for someone
#Boys are between 1 meter and 1.5 meters. Xiaoqiang, where are you?
#Boys have no sense of security between 1.5 and 1.7 meters~
#Boys between 1.7 and 1.8 meters leave a phone call
#Boys are handsome between 1.8 and 2 meters. Do you suggest having another girlfriend

# General writing method
height = float(input("Please enter your height:"))
if 1 <= height and height < 1.5:
    print("Xiaoqiang, where are you?")
elif 1.5 <= height and height < 1.7:
    print("No sense of security~")
elif 1.7 <= height and height < 1.8:
    print("Handsome guy, leave a phone")
elif 1.8 <= height and height < 2:
    print("Do you suggest having another girlfriend")
else:
    print("i 'm sorry,There are no suitable options")

Shortcut key usage:
Indent right
shift + tab indent left

Cyclic structure

Features: reduce redundant code and improve execution efficiency

Syntax:

while conditional expression:

　　code1

(1) Initialize a variable

(2) Write the condition of the loop

(3) Self increasing and self decreasing value

Print 1 ~ 100

# (1) Initialize a variable
i = 1
# (2) Write the condition of the loop
while i <= 100:

    # (4) Write the logic of the loop
    print(i)

    # (3) Self increasing and self decreasing value
    i += 1 # i = i + 1

"""
Code parsing:
First cycle
i = 1  i<=100 Judge as true,Execution loop body print(1)
i += 1 i => 2 
Second cycle
The code goes back to line 17,Condition determination again 
i = 2  i<=100 Judge as true,Execution loop body print(2)
i += 1 i => 3
Third cycle
The code goes back to line 17,Condition determination again 
i = 3  i<=100 Judge as true,Execution loop body print(3)
i += 1 i => 4

....
and so on 

until i = 101  i <= 100 Judged as false,Do not execute loop body,This is the end of the cycle...
1 ~ 100
"""

Sum of 100 ~ 1

# (1) Initialize a variable
i = 1
total = 0

# (2) Write the condition of the loop
while i <= 100 :
    # (4) Write custom logic
    total += i
    # (3) Self increasing and self decreasing value
    i += 1
print(total)


"""
Code parsing:
First cycle
i = 1 i <= 100 Judged to be true True Execution loop body total += i => total = total + i => 0 + 1
i += 1  => i = 2

Second cycle
i = 2 i <= 100 Judged to be true True Execution loop body total += i => total = total + i => 0 + 1 + 2
i += 1  => i = 3

Third cycle
i = 3 i <= 100 Judged to be true True Execution loop body total += i => total = total + i => 0 + 1 + 2 + 3 
i += 1  => i = 4

...
And so on

When i = 101 101 <= 100 Judged as false False Do not execute loop body,Here we are,End of cycle..

total += i => total + i => 0 + 1 + 2 + 3 + 4 + .... + 100 => 5050

"""

Dead cycle

"""

while True:

　　print(1)

"""

Using the method of dead cycle to realize the accumulation and sum of 1 ~ 100

i = 1
total = 0
sign = True
while sign:
    total += i
    i+=1
    
    # Judge whether i is added to 101 and does not participate in the cycle
    if i == 101:
        # Terminate cycle
        sign = False
print(total) #1 ~ 100 = 5050

One way circular exercise

(1) Print a line with a little star * help(print)

#help view the documentation of a method

help(print)

"""
# print("*",end='')
# print("*",end='')
# print("*",end='')
# print("*",end='')
# print("*",end='')
# print("*",end='')
# print("*",end='')
# print("*",end='')
# print("*",end='')
# print("*",end='')
"""

If the above method is not only a lot of code, but also too stupid, let's use the while loop

i = 0
while i<10:    
    # End = 'when printing, there is no line break at the end by default
    print("*",end='')    
    i += 1
# Default Wrap
# print()

(2) By printing a variable, show a row of ten small stars

print("<======>")
i = 0
strvar = ""
while i < 10:
    # Write the logic of the loop
    strvar += "*" # strvar = strvar + "*"
    i +=1
print(strvar)


process:
"""
strvar += "*" => strvar = "*"
strvar += "*" => strvar = "*" + "*"  = "**"
strvar += "*" => strvar = "**" + "*" = "***"
...
strvar += "*" => strvar = "********" + "*" = "*********"
"""

(3) A row of ten stars with different colors ★★★★★★★★★★★★

Method 1:

i = 0
while i < 5:
    print("★☆",end="")
    i+=1

Method 2:

i = 0
while i < 10:
    if i % 2 == 0 :
        print("★",end="")
    else:
        print("☆",end="")
    i+=1

Method 3:

i = 0
strvar = ""
while i < 10:
    if i % 2 == 0 :
        strvar += "★"
    else:
        strvar += "☆"
    i+=1
print(strvar)

***Formula: any number and N are used for remainder. The range of remainder: 0 ~ (n-1)***
0 % 2 = 0
1 % 2 = 1
2 % 2 = 0
3 % 2 = 1
Dividend% 2 = > 0 or 1

0 % 5 = 0 
1 % 5 = 1
2 % 5 = 2
3 % 5 = 3
4 % 5 = 4
5 % 5 = 0 
6 % 5 = 1
7 % 5 = 2
Dividend% 5 = > 0 or 1,2,3,4

(4) Print ten rows and ten columns of small stars in one cycle

"""

★★★★★★★★★★

★★★★★★★★★★

★★★★★★★★★★

★★★★★★★★★★

★★★★★★★★★★

★★★★★★★★★★

★★★★★★★★★★

★★★★★★★★★★

★★★★★★★★★★

★★★★★★★★★★