Python Basics: Numbers, Strings, Functions, Data Structures, Classes, and Tools

This tutorial introduces essential Python concepts, starting with numeric operations such as absolute value, base conversions, complex numbers, and arithmetic utilities like abs , bin , oct , hex , divmod , round , and pow . It also demonstrates logical checks using all and any , and boolean conversion with bool .

<code>In [1]: abs(-6)
Out[1]: 6
In [2]: bin(10)
Out[2]: '0b1010'
In [3]: oct(9)
Out[3]: '0o11'
In [4]: hex(15)
Out[4]: '0xf'
In [5]: divmod(10, 3)
Out[5]: (3, 1)
In[6]: round(10.0222222, 3)
Out[6]: 10.022
In[7]: pow(3, 2, 4)
Out[7]: 1
</code>

String handling examples include converting strings to bytes, casting objects to strings, executing code stored in strings, evaluating expressions, and formatting output with format :

<code>In [12]: s = "apple"
In [13]: bytes(s, encoding='utf-8')
Out[13]: b'apple'
In [14]: str(100)
Out[14]: '100'
In [15]: exec(compile("print('helloworld')", "<string>", "exec"))
helloworld
In [16]: eval("1 + 3 + 5")
Out[16]: 9
In [18]: "i am {0},age{1}".format("tom", 18)
Out[18]: 'i am tom,age18'
</code>

Function utilities cover built‑in functions such as sorted , sum , and custom functions demonstrating variable arguments, keyword‑only arguments, and lambda expressions:

<code>def max_len(*lists):
    return max(*lists, key=lambda v: len(v))

max_len([1,2,3], [4,5,6,7], [8])  # returns the longest list
</code>

Data‑structure sections show how to create dictionaries, frozensets, sets, slices, tuples, and how to convert between them:

<code>dict(a=1, b=2)
frozenset([1,1,3,2,3])
set([1,4,2,3,1])
slice(1,10,2)
tuple([1,3,5])
</code>

The class and object part explains defining classes, using __init__ , __repr__ , checking callability, adding attributes dynamically, using classmethod , property decorators, and introspection functions like callable , hasattr , getattr , isinstance , issubclass , and type :

<code>class Student:
    def __init__(self, id, name):
        self.id = id
        self.name = name
    def __repr__(self):
        return f'id = {self.id}, name = {self.name}'

xiaoming = Student('001', 'xiaoming')
print(callable(xiaoming))  # False
print(hasattr(xiaoming, 'name'))  # True
</code>

Tools covered include enumeration, size inspection with sys.getsizeof , filtering with filter , hashing with hash , help documentation, file I/O with open , range generation, reversed iteration, zip aggregation, chained operations, and JSON serialization of objects:

<code>import sys
sys.getsizeof({"a":1, "b":2.0})  # 240 bytes

filtered = filter(lambda x: x>10, [1,11,2,45,7,6,13])
list(filtered)  # [11, 45, 13]

with open('json.txt', 'w', encoding='utf-8') as f:
    json.dump([xiaoming, xiaohong], f, default=lambda obj: obj.__dict__, ensure_ascii=False, indent=2)
</code>

Overall, the article serves as a practical reference for Python beginners and intermediate users, illustrating core language features and common utilities with ready‑to‑run code snippets.