-Code block

Start with a colon and use indentation to divide the same scope, called a code block, a code block as a whole, or a file as a code block
Scope: The area of action
Other languages use {} to divide scopes, while python uses code blocks
python code blocks can improve overall integrity and development efficiency

# python
if 5 == 5:
    print(1)
    print(2)

if True:
    print(3)
    print(4)


if False:
    print(5)
    print(6)
    print(7)

# php c js
if(False){
	print(5)
				print(6)
}

Note: Either use all 4 spaces or all 1 indent so that the same scope cannot be mixed up

Process Control

1. Definition of process control
   Process: The process of code execution
   Process Control: Manage the process of code execution
2. Structure of process control
   Sequential structure: code is executed top-down by default
   Branch structure: subdivided as follows
   Loop structure: while...for...

Branch structure

Keyword: if elif else

• Types of branching structures

1. Single Branch
2. Binomial Branch
3. Multiple Branches
4. Nested Branch

• Characteristics of Branch Structure

Single Branch

if  Conditional expression:
	code1
	code2

If the conditional expression is true, return True to execute the following code block,
If the conditional expression is not valid, return False without executing the following code block

zhangyaowen = "Handsome guy"

if zhangyaowen == "Handsome guy":
    print("Please have a kebab")
    print("Have a beer")
    print("Please eat a large waist")

Binomial Branch

if Conditional expression:
	code1
	code2
else:
	code3
	code4

If the conditional expression is valid, execute the code block below if
If the conditional expression is not valid, execute the code block below else

Code blocks in if can be called true intervals
Code blocks in else can be called pseudo-intervals

zhangyaowen = "Beast"
if zhangyaowen == "Blind Flow":
    print("Hit him")
    print("Pinch him")
    print("hung up,Feed him chili water")
else:
    print("Coax him")
    print("Love him")
    print("Defraud him of the money in his pocket")

# Input waits for user input string
res = input("Please enter your name:")
print(res, type(res))

username = input('please enter your username:')
pswd = input('please enter your password:')
if username == 'admin' and pswd == '000':
    print('Landing Success!')
else:
    print('Wrong login or password entry,Logon Failure!')

Multiple Branches

f Conditional expression 1:
	code1
	code2
elif Conditional expression 2:
	code3
	code4
elif Conditional expression 3:
	code5
	code6	
...
	
else:
	code7

If conditional expression 1 is true, execute the code block in if if if it is not
Judge down one by one to see if conditional expression 2 is valid, then execute the corresponding code block.
Conversely, continue to judge conditional expression 3 down, if the corresponding block of execution code is established.
Conversely, proceed down to determine if none of the conditions are met and execute the code block in else directly

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

if youqian == True:
	print("I will marry him 1")
elif youfang == True:
	print("I will marry him 2")
elif youche == True:
	print("I will marry him 3")
elif youyanzhi == True:
	print("I will marry him 4")
elif youtili == True:
	print("I will marry him 5")
else:
	print("Let's go, man,No. 2 car will catch up in a while 6")

Nested Branch

(Single Branch Binomial Branch Multiple Branches Nested with each other)

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

if youqian == True:
	if youfang == True:
		if youche == True:
			if youyanzhi == True:
				if youtili == True:
					print("You are my favorite Langjun,1")
				else:
					print("Congratulations,My number 1 spare birth2")
			else:
				print("I have never had a relationship with an ugly person,No Fate 3")
				
else:
	print("You're a great person Ah 4")

Cyclic structure

Keyword: while / for...in...

• Types of circular structure

1. while loop
2. for loop

• Characteristics of the cycle structure

while loop

Can improve the efficiency of code, reduce code redundancy

while Conditional expression:
	code1
	code2

If the conditional expression is valid and returns True, the block of code in it is executed

Basic Syntax: Print 1 ~ 100

# (1) Initialization variable i
i = 1
 # (2) Write cyclic criteria
while i <= 100:
    print(i)
    # (3) Self-increasing and self-decreasing conditions
    i += 1
"""
#Code parsing:
Initialize i = 1 first
 Then judge that 1<=100 satisfies the return True execution block
 Then print(1)
i+=1 i = i+1 i=> 2

To go back to the conditional expression to make a judgment is to go back to 16 lines
 2 <= 100 satisfies the return True execution block
 Then print(2)
i+=1 i = i+1 2+1 i =>3

To go back to the conditional expression to make a judgment is to go back to 16 lines
 3 <= 100 satisfies the return True execution block
 Then print(3)
i+=1 i = i+1 3+1 i =>4

...
...
When do you jump out of the condition?
When i = 101
 101 <= 100 does not satisfy returning False without executing code block
 Loop termination...
"""

The sum of 1~100

# (1) First method
i = 1
total = 0
while i <= 100:
    # Write Logic
    # print(i)
    total += i
    i += 1
print(total)

'''
# Code parsing:

total += i => total = total + i => 0 + 1 => 1
i+=1 => i = i+1 => 1+1 => 2
2 <= 100 Satisfy Return True True

total += i => totoal = total + i => 0 + 1 + 2 => 3
i+=1 => i = i+1 => 2+1 => 3
3 <= 100 Satisfy Return True True

total += i => totoal = total + i => 0 + 1 + 2 + 3 => 6
i+=1 => i = i+1 => 3+1 => 4
4 <= 100 Satisfy Return True True

total += i => totoal = total + i => 0 + 1 + 2 + 3 + 4 + 5 + ...+ 100 => 5050

//When i = 101
101 <= 100 Not satisfied with cycle termination...

'''

# (2) Dead-cycle writing
# while True:
# print(1)

i = 1
flag = True
total = 0
while flag:
    total += i
    i += 1
    # Add a condition to jump out of
    if i == 101:
        flag = False

print(total)

for loop

String-related operations

1. String Stitching

   strvar1 = "I love you,"
   strvar2 = "Dear Mushroom Cool"
   res = strvar1 + strvar2
   print(res)
   
   

2. Repetition of strings

   strvar1 = "Important things are to be repeated for 3 times"
   res = strvar1 * 3
   print(res)
   

3. String splicing across lines

   str1 = "sdfsssssssssssssssssssssssssssssssssssssssssssss" \
       "sssdsfsdfasdf" \
       "Your Speak Hand"
   print(str1)
   

4. Index of strings

   #         0 1 2 3 4 5
   strvar = "The road is bright"
   #        -6-5-4-3-2-1
   res = strvar[4]
   print(res)
   res = strvar[-2]
   print(res)