Python basic code collection

Python is an easy-to-learn, powerful programming language that is widely used in various fields, from data analysis to web development, from artificial intelligence to scientific computing. The following is a complete collection of Python basic codes:

1. Basic syntax

1. Print output

print("Hello, World!")

2. Variable assignment

x = 10
y = "Hello"

3. Conditions Statement

if x > 5:
    print("x大于5")
elif x == 5:
    print("x等于5")
else:
    print("x小于5")

4. Loop statement

for i in range(5):
    print(i)
    
while x > 0:
    print(x)
    x -= 1

5. Function definition

def add(x, y):
    return x + y

6. Exception handling

try:
    # 可能发生异常的代码
    result = 10 / 0
except ZeroDivisionError:
    # 处理异常的代码
    print("除数不能为零")

2. Data type

1. Number type

x = 10
y = 3.14
z = complex(1, 2)

2. String type

s = "Hello, World!"
print(s[0])  # 输出第一个字符
print(s[7:12])  # 输出从第8个字符到第12个字符

3. List type

lst = [1, 2, 3, 4, 5]
print(lst[0])  # 输出第一个元素
print(lst[2:4])  # 输出第3个元素到第4个元素

4. Tuple type

tpl = (1, 2, 3, 4, 5)
print(tpl[0])  # 输出第一个元素
print(tpl[2:4])  # 输出第3个元素到第4个元素

5. Dictionary Type

dic = {"name": "Tom", "age": 18}
print(dic["name"])  # 输出键为"name"的值
print(dic.keys())  # 输出所有键
print(dic.values())  # 输出所有值

6. Collection type

s = {1, 2, 3, 4, 5}
s.add(6)  # 添加元素
s.remove(3)  # 移除元素

3. File operation

1. Open the file

f = open("file.txt", "r")

2. Read the file content

content = f.read()
print(content)

3. Write the file content

f.write("Hello, World!")

4. Close the file

f.close()

4. Functions and modules

1. Custom functions

def add(x, y):
    return x + y

2. Import module

import math
print(math.sqrt(16))  # 输出平方根

3. Use third-party library

import requests
response = requests.get("https://www.example.com")
print(response.text)  # 输出网页内容

5. Object-oriented programming

1. Define class

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age
        
    def say_hello(self):
        print("Hello, I'm", self.name)
        
p = Person("Tom", 18)
p.say_hello()

2. Inheritance and Polymorphism

class Student(Person):
    def __init__(self, name, age, grade):
        super().__init__(name, age)
        self.grade = grade
        
    def say_hello(self):
        print("Hello, I'm", self.name, "and I'm in grade", self.grade)
        
s = Student("Jerry", 16, 10)
s.say_hello()

6. Common libraries and frameworks

1. Data processing and analysis

import pandas as pd
df = pd.DataFrame({"name": ["Tom", "Jerry"], "age": [18, 16]})
print(df.head())

2. Web development

from flask import Flask
app = Flask(__name__)
@app.route("/")
def hello():
    return "Hello, World!"
if __name__ == "__main__":
    app.run()

3. Machine learning

from sklearn.linear_model import LinearRegression
model = LinearRegression()
model.fit(X, y)

4. Image processing

from PIL import Image
im = Image.open("image.jpg")
im.show()

The above are just a small sample of the basic code of Python. The Python language is powerful and there are many other usages and libraries that can be explored. Hope these codes help you, if you have any questions please feel free to let me know and I will try to help.

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