print("3*2") output is 3*2

print(3*2) output result is 6

print("this is 3X2 result:{3 * 2} ") this is 3X2 result:{3 * 2}

f: There is a special format {}: The inside is not affected by double quoted string types

type("2.8") returns str

type(2.8) returns floats

[ ] Represents an array

Call a number in the array individually and count from 0

Add an array

# Create a dictionary containing three key-value pairs person = {"name": "Alice", "age": 25, "city": "New York"}

# Create a dictionary through keyword parameters student = dict(name="Bob", grade=80) # Create a dictionary from a list containing a tuple of key-value pairs colors = dict([("red", 1), ("green", 2), ("blue", 3)])

person = {"name": "Alice", "age": 25, "city": "New York"} print(person["name"]) # Output: Alice

person = {"name": "Alice", "age": 25} # Add elements person["city"] = "New York" # Modify elements person["age"] = 26 print(person) # Output: {'name': 'Alice', 'age': 26, 'city': 'New York'}

person = {"name": "Alice", "age": 25, "city": "New York"} del person["city"] print(person) # Output: {'name': 'Alice', 'age': 25}

is a variable ordered sequence, represented by square brackets [].

my_list = [1, 2, 3, 4] my_list.append(5)

is an immutable ordered sequence, represented by parentheses ().

my_tuple = (1, 2, 3)

is an unordered set of key-value pairs, represented by curly braces {}

my_dict = {"name": "Alice", "age": 20} print(my_dict["name"])

is a collection of unordered and unique elements, created with curly braces {} or set() functions.

my_set = {1, 2, 3, 3} print(my_set)

Spaces are very important and represent the scope of function function.

if: else:

elif: Allows multiple condition branches to be added after an if statement. The program will check each elif condition in turn. Once a condition is true, the corresponding code block will be executed and the subsequent elif or else conditions will no longer be checked.

else: used to deal with all cases where the previous if and elif conditions are not met. It does not require specifying additional conditions, as long as all previous conditions are false, the contents in the else code block will be executed.

for in statement loop execution

enumerate: index of the sequence. index is an index value generated by the enumerate() function

Index values ​​are very important and can trigger an operation at a certain location.

== is a comparison operator

a = 1 b = 2 print(a>b) False

Addition, used to add or splice two numbers 5 3 The result is 8; "Hello " "World" The result is "Hello World" - Subtraction, used to subtract two numbers 5 - 3 The result is 2 * Multiplication, used to multiply two numbers or repeat sequences 5 * 3 The result is 15; "abc" * 3 The result is "abcabcabc" / division, return floating point result 5 / 3 The result is 1.66666666666666666666667 // Divide, return the integer part of the quotient 5 // 3 The result is 1 % Take the modulus and return the remainder of the division 5 % 3 The result is 2 ** Power operation, calculate the specified power of a number 5 ** 3 The result is 125

a = 1 b = 2 print((a or b) >1) False

in If the value is in a sequence, set, or dictionary (judgment key), return True 3 in [1, 2, 3] The result is True not in If the value is not in a sequence, set, or dictionary (judgment key), return True 4 not in [1, 2, 3] The result is True

is Determine whether two objects are the same object a = [1, 2]; b = a; a is b The result is True is not to determine whether two objects are not the same object a = [1, 2]; b = [1, 2]; a is not b The result is True

After reading, use it with the closed file to free up memory

Use with more in actual work, and you can automatically close it after reading it.

If the file does not exist, a FileNotFoundError exception will be thrown. This exception can be caught and handled using the try-except statement.

The input() function is used to get input from the user and return the contents entered by the user as a string.

The float() function converts the string entered by the user into a floating point number for numerical calculations.