Python Variable Usage, Types, and Naming Conventions

1. Using Variables: The following code reads a number the user thinks of and prints it.

<code>number = input("你想到了什么数字? ")
print("你想到的数字是:", number)</code>

The first line uses input() to read console input into the variable number , and the second line prints the variable's value.

2. Variable Types: To output the square of the number, the code number * number would raise an error because input() returns a string. Converting the string to an integer with int() resolves the issue.

<code>number = input("你想到了什么数字? ")
print("你想到数字的平方是:", int(number) * int(number))</code>

Common Python variable types include:

int: arbitrary-size integers

float: arbitrary-precision floating‑point numbers

str: text strings

bool: True or False

complex: complex numbers (real + imag)

3. Checking Variable Types: The type() function can be used to inspect a variable's type.

<code>var_1 = 3
var_2 = 3.1415926
var_3 = 2 + 1j
var_4 = "Hello World"
var_5 = True
print(type(var_1))  # <class 'int'>
print(type(var_2))  # <class 'float'>
print(type(var_3))  # <class 'complex'>
print(type(var_4))  # <class 'str'>
print(type(var_5))  # <class 'bool'>
</code>

4. Type Conversion: Functions like int() and str() can convert values between types.

<code>var = 3.1415926
print(type(int(var)), int(var))  # <class 'int'> 3
print(type(str(var)), str(var))  # <class 'str'> 3.1415926
</code>

5. Variable Naming Rules: Variable names must start with a letter or underscore and consist of letters, digits, or underscores; they cannot be Python keywords. The convention is lowercase with underscores (e.g., this_is_variable ), while global constants are uppercase.