Master Python’s Core Data Types: Numbers, Strings, Lists, and More

Fundamental Data Types in Python

Introduction

Hello everyone, when first learning Python you may encounter many difficulties. This article summarizes Python’s basic data types for easy reference and memorization.

Python Data Types

Number (numeric)

String (text)

List

Tuple

Set

Dictionary

Classification

Immutable: Number, String, Tuple

Mutable: List, Dictionary, Set

Variable Operations in Python

Python supports multiple assignment, e.g.:

a = b = c = 1</code>
<code>print(a)</code>
<code>print(b)</code>
<code>print(c)

Now a, b, c are all 1.

Multiple assignment with different values:

a, b, c = 1, 2, 3</code>
<code>print(a)</code>
<code>print(b)</code>
<code>print(c)

Swap variables without a temporary variable:

a = 1</code>
<code>b = 2</code>
<code>a, b = b, a</code>
<code>print(a)</code>
<code>print(b)

Other languages often need a temporary variable:

a = 1  # assign</code>
<code>b = 2  # assign</code>
<code>c = a  # store a</code>
<code>a = b  # a gets b</code>
<code>b = c  # b gets original a</code>
<code>print(a)</code>
<code>print(b)

Inspecting Data Types

Use type(x) to view a variable’s type:

a, b, c = 1, True, 1.0</code>
<code>print(type(a), type(b), type(c))  # <class 'int'> <class 'bool'> <class 'float'>

a, b, c = '1', 'True', '1.0'</code>
<code>print(type(a), type(b), type(c))  # <class 'str'> <class 'str'> <class 'str'>

Number

Conversion examples:

temp = '123'  # non‑numeric string will cause error if converted directly</code>
<code>print(type(temp))  # <class 'str'></code>
<code>res = int(temp)</code>
<code>print(type(res), res)  # <class 'int'> 123

temp = "b"</code>
<code>res = int(temp, base=16)  # specify base, default is 10</code>
<code>print(type(res), res)

Comparison examples:

print(1 == True)  # True</code>
<code>print(0 == False)  # True

Common numeric functions:

abs(x)      # absolute value</code>
<code>ceil(x)    # round up</code>
<code>exp(x)     # e to the power x</code>
<code>fabs(x)    # absolute value (float)</code>
<code>floor(x)   # round down</code>
<code>log(x)     # natural logarithm (x > 0)</code>
<code>log10(x)   # base‑10 logarithm</code>
<code>max(... )  # maximum value</code>
<code>min(... )  # minimum value</code>
<code>pow(x, y)  # x**y</code>
<code>round(x, n) # round to n decimal places</code>
<code>sqrt(x)    # square root

String

Length

temp = 'hahahahahahaha'</code>
<code>print(len(temp))  # 14

Slicing

# [start:stop:step]</code>
<code>temp = "abcdefg"</code>
<code>res1 = temp[::]      # abcdefg</code>
<code>res2 = temp[0:-1:2]  # ace

Formatting

# default positional formatting</code>
<code>temp1 = "I am {}, I am {} years old!"</code>
<code>res1 = temp1.format('Xianyu', 22)</code>
<code>print(res1)  # I am Xianyu, I am 22 years old!</code>
<code># indexed formatting</code>
<code>temp2 = "I am {1}, I am {0} years old!"</code>
<code>res2 = temp2.format('Xianyu', 22)</code>
<code>print(res2)  # I am 22, I am Xianyu years old!</code>
<code># named formatting</code>
<code>temp3 = "I am {name}, I am {age} years old!"</code>
<code>res3 = temp3.format(name='Xianyu', age=22)</code>
<code>print(res3)  # I am Xianyu, I am 22 years old!

find

# find first occurrence, returns index or -1</code>
<code>temp = "hahe"</code>
<code>res = temp.find("h", 1, 3)</code>
<code>print(res)

lower

temp = "AAAaaaBBbb"</code>
<code>res = temp.lower()</code>
<code>print(res)  # aaaaaabbbb

upper

temp = "abc"</code>
<code>res = temp.upper()</code>
<code>print(res)  # ABC

strip

# remove leading/trailing whitespace (including newlines and tabs)</code>
<code>temp = "     a aa   
 "</code>
<code>res = temp.strip()</code>
<code>print(res)  # a aa

join

# join characters with a separator</code>
<code>temp1 = 'abcd'</code>
<code>temp2 = '-'</code>
<code>res1 = temp2.join(temp1)</code>
<code>print(res1)  # a-b-c-d</code>
<code># simple concatenation</code>
<code>temp3 = 'abc'</code>
<code>temp4 = '123'</code>
<code>res3 = temp3 + temp4</code>
<code>print(res3)  # abc123

replace

# replace substring</code>
<code>temp = 'hahahaha'</code>
<code>res = temp.replace("a", "e", 50)</code>
<code>print(res)  # hehehehe