Python Basics

After building several Java AI projects, I noticed that the demand for Python AI application development is broader in the market. Although I did use Python before, most of it was done through vibe coding, so my fundamentals were not solid. I am using this chance to systematically fill in Python basics.

Basic Variables and Syntax Style

I first defined a few variables:

money = 50.1
name = "小明"
age = 18

Compared with Java, the most direct differences are:

• No ;
• No main-class entry structure
• No explicit variable type declaration when defining variables

for Loop and String Formatting

for i in range(4):
    print(f"{i + 1} hello world")

I used f-string here. Also, print can use comma-separated arguments:

print("money:", money)

My understanding is that this style is more direct and avoids frequent string concatenation as in Java.

Boolean Values and if/else

sig1 = True
sig2 = False

if sig2:
    print("sig2 is true")
else:
    print("sig2 is false")

I also noticed Python is highly indentation-sensitive. The if/else block is fully defined by indentation levels.

Functions and Type Inspection

def print_type(x):
    print(type(x))

print_type(money)
print_type(name)
print_type(age)

At this stage, I mainly used this to get familiar with:

• Function definitions without mandatory return type declarations
• Using type() to quickly inspect the real runtime type of variables

Type Conversion

a = 123
print("a", type(str(a)))

This verifies numeric-to-string conversion using str(a).

Identifier and Naming Rules

The key rules I memorized today are:

• Identifiers can consist of Chinese/English characters, digits, and underscores
• They cannot start with a digit
• They cannot use Python keywords
• Python is case-sensitive

Variable naming convention:

• Use lowercase letters
• Use underscores for multi-word names (snake_case)

Invalid naming examples:

• 1name
• Names with special symbols such as name!, name@, name#, etc.

Stage Summary

• First, remove Java-style boilerplate thinking
• Then, get used to Python indentation and dynamic typing
• Then, master the most common basics: loops, conditions, functions, and type conversion

Next, I will continue with lists/dicts, object-oriented programming, file handling, and common AI development libraries.