Master Python Variables and 4 Core Data Types in 5 Minutes

1. Variables (quick copy‑paste)

# Direct copy, run to see effect
name = "张三"  # store name
age = 20      # store age
height = 175.5  # store height
is_student = True  # store boolean

print(name)
print(age, height)
print(is_student)

Definition rule: variable_name = data (no spaces, cannot start with Chinese characters, cannot use keywords). Variable names should be meaningful, e.g., use age for age.

2. Four core data types

String ( str): text enclosed in single or double quotes.

Integer ( int): whole numbers without a decimal point.

Float ( float): numbers with a decimal point.

Boolean ( bool): two values True or False, used for logical tests.

3. Common beginner pitfalls and fixes

Pitfall 1: Variable name syntax errors (e.g., starting with Chinese characters or containing spaces). Fix: Use only ASCII letters, digits, and underscores, and avoid leading digits.

Pitfall 2: Trying to concatenate strings and numbers directly (e.g., print("Age:" + 20)). Fix: Convert numbers to strings: print("Age:" + str(age)).

Pitfall 3: Installing packages with a mirror that fails to parse the webpage. Fix: Use the Tsinghua mirror first:

pip install -i https://pypi.tuna.tsinghua.edu.cn/simple 包名

, or fall back to Aliyun mirror if needed.

4. After‑class exercises (5 minutes)

# 1. Define three variables (name, age, weight) and print them
name = "李四"
age = 18
weight = 62.5
print("姓名：", name, "年龄：", age, "体重：", weight)

# 2. Compute weight*2 + 10, keep one decimal, and print
result = weight * 2 + 10
print(round(result, 1))

# 3. Check whether age is greater than 18 and print the boolean result
print(age > 18)

Key takeaways

Variables store data; the four types map to different scenarios: text, integer, decimal, and logical judgment.

Essential today: variable definition plus common string and integer operations.

When errors occur, first check variable‑naming rules, data‑type concatenation, and package‑mirror selection.