10 Classic Python Operations: Variables, Type Conversion, Strings, Lists, Loops, Conditionals, Functions, Exceptions, File I/O, and Modules

Python is a concise and powerful language widely used for data processing, AI, and web development; this tutorial presents ten classic operations to enhance your coding skills.

1. Variable Assignment and Swapping

Assign values with the = operator and swap two variables in a single line using tuple unpacking.

a = 5
b = "Hello, Python!"

a = 3
b = 4
a, b = b, a
print(a)  # 4
print(b)  # 3

2. Data Type Conversion

Convert between common types using built‑in functions such as int() , float() , str() , and list() .

num_str = "123"
num_int = int(num_str)
print(num_int)  # 123

num = 5
num_float = float(num)
print(num_float)  # 5.0

num = 42
num_str = str(num)
print(num_str)  # "42"

string = "python"
string_list = list(string)
print(string_list)  # ['p', 'y', 't', 'h', 'o', 'n']

3. String Operations

Concatenate strings with + or join() , and format them using format() or f‑strings.

str1 = "Hello"
str2 = "World"
result = str1 + " " + str2
print(result)  # "Hello World"

words = ["Python", "is", "awesome"]
result = " ".join(words)
print(result)  # "Python is awesome"

name = "Alice"
age = 25
message = "My name is {} and I'm {} years old.".format(name, age)
print(message)

name = "Bob"
age = 30
message = f"My name is {name} and I'm {age} years old."
print(message)

4. List Operations

Use append() , extend() , indexing, assignment, and slicing to manipulate lists.

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

list1 = [1, 2]
list2 = [3, 4]
list1.extend(list2)
print(list1)  # [1, 2, 3, 4]

my_list = ["apple", "banana", "cherry"]
print(my_list[1])  # "banana"
my_list[2] = "date"
print(my_list)  # ["apple", "banana", "date"]

my_list = [1, 2, 3, 4, 5]
sub_list = my_list[1:3]
print(sub_list)  # [2, 3]
sub_list = my_list[::2]
print(sub_list)  # [1, 3, 5]

5. Loop Constructs

Iterate with for loops over iterables or a range, and repeat with while loops.

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

for i in range(5):
    print(i)

count = 0
while count < 3:
    print(count)
    count += 1

6. Conditional Statements

Use if‑elif‑else to branch logic, including nested conditions.

num = 10
if num > 0:
    print("正数")
elif num == 0:
    print("零")
else:
    print("负数")

age = 18
has_id = True
if age >= 18:
    if has_id:
        print("可以进入酒吧")
    else:
        print("请出示身份证")
else:
    print("未满18岁，禁止入内")

7. Function Definition and Invocation

Define reusable code blocks with def and call them with arguments.

def add_numbers(a, b):
    return a + b
result = add_numbers(3, 5)
print(result)  # 8

8. Exception Handling

Protect code with try‑except to catch runtime errors such as division by zero.

try:
    num1 = 10
    num2 = 0
    result = num1 / num2
except ZeroDivisionError:
    print("除数不能为零")

9. File Operations

Read and write files using open() with context managers.

try:
    with open('example.txt', 'r') as file:
        content = file.read()
        print(content)
except FileNotFoundError:
    print("文件未找到")

with open('output.txt', 'w') as file:
    file.write("Hello, this is a new line.")

with open('output.txt', 'a') as file:
    file.write("\nThis is an appended line.")

10. Module Import

Leverage standard and third‑party libraries by importing them.

import math
result = math.sqrt(16)
print(result)  # 4.0

from datetime import datetime
now = datetime.now()
print(now)

By mastering these ten classic Python operations, you lay a solid foundation for more advanced programming tasks and can confidently apply these techniques to solve real‑world problems.