Python初学者指南：数据结构与算法详解

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"《问题求解与算法与数据结构》是一本专门针对Python编程初学者设计的电子学习资料，它深入浅出地讲解了数据结构和算法的基本概念以及它们在Python中的应用。本书第三版由Brad Miller和David Ranum编著，发布日期为2013年9月22日。第一章介绍了学习目标，包括了解计算机科学的目的、回顾Python基础知识，以及设置一系列的编程练习，帮助读者建立起扎实的编程基础。这一章旨在引导读者理解和掌握解决问题的基本思路和方法。第二章主要聚焦于算法分析，解释了算法分析的含义，讨论了Python数据结构的性能优化。通过深入剖析，读者将理解如何评估算法效率，并通过讨论问题来提升对算法的理解。该部分也包含丰富的编程练习，使理论与实践相结合。第三章详细讲解了基本数据结构，如线性结构、栈、队列、双端队列（deque）、列表等。作者分别阐述了这些数据结构的概念、抽象数据类型及其Python实现。通过实例，读者能够掌握如何利用这些结构进行数据组织和操作。第四章探讨了递归这个重要的概念，解释递归的本质，以及如何通过栈来实现递归调用。通过视觉化的演示，读者可以更好地理解递归的逻辑和工作原理。每一章都以明确的学习目标引领，通过实例和习题强化理解，使得初学者能够在实践中逐渐提升Python编程技能，尤其在数据结构和算法方面。尽管书中的一些内容对初学者来说可能具有挑战性，但通过系统学习，他们能够逐步掌握这一领域的核心知识。这本书是Python程序员成长过程中不可或缺的参考资料，无论是自学还是教学，都能提供有价值的知识和实践指导。"

Problem Solving with Algorithms and Data Structures, Release 3.0

Method Name Use Explanation

append a_list.append(item) Adds a new item to the end of a list

insert a_list.insert(i,item) Inserts an item at the 𝑖

position in a list

pop a_list.pop() Removes and returns the last item in a list

pop a_list.pop(i) Removes and returns the 𝑖

item in a list

sort a_list.sort() Modiﬁes a list to be sorted

reverse a_list.reverse() Modiﬁes a list to be in reverse order

del del a_list[i] Deletes the item in the 𝑖

position

index a_list.index(item) Returns the index of the ﬁrst occurrence of item

count a_list.count(item) Returns the number of occurrences of item

remove a_list.remove(item) Removes the ﬁrst occurrence of item

Table 1.3: Methods Provided by Lists in Python

following session:

my_list = [1,2,3,4]

A = [my_list]

print(A)

my_list[2]=45

print(A)

The variable A holds a collection of three references to the original list called my_list. Note

that a change to one element of my_list shows up in all three occurrences in A.

Lists support a number of methods that will be used to build data structures. Table 1.3 provides

a summary. Examples of their use follow.

my_list = [1024, 3, True, 6.5]

my_list.append(False)

print(my_list)

my_list.insert(2,4.5)

print(my_list)

print(my_list.pop())

print(my_list)

print(my_list.pop(1))

print(my_list)

my_list.pop(2)

print(my_list)

my_list.sort()

print(my_list)

my_list.reverse()

print(my_list)

print(my_list.count(6.5))

print(my_list.index(4.5))

my_list.remove(6.5)

print(my_list)

del my_list[0]

print(my_list)

12 Chapter 1. Introduction

Problem Solving with Algorithms and Data Structures, Release 3.0

You can see that some of the methods, such as pop, return a value and also modify the list.

Others, such as reverse, simply modify the list with no return value. pop will default to

the end of the list but can also remove and return a speciﬁc item. The index range starting

from 0 is again used for these methods. You should also notice the familiar “dot” notation

for asking an object to invoke a method. my_list.append(False) can be read as “ask the

object my_list to perform its append method and send it the value False.” Even simple

data objects such as integers can invoke methods in this way.

>>> (54).__add__(21)

>>>

In this fragment we are asking the integer object 54 to execute its add method (called __add__

in Python) and passing it 21 as the value to add. The result is the sum, 75. Of course, we usually

write this as 54 + 21. We will say much more about these methods later in this section.

One common Python function that is often discussed in conjunction with lists is the range

function. range produces a range object that represents a sequence of values. By using the

list function, it is possible to see the value of the range object as a list. This is illustrated

below.

>>> range(10)

range(0, 10)

>>> list(range(10))

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> range(5,10)

range(5, 10)

>>> list(range(5,10))

[5, 6, 7, 8, 9]

>>> list(range(5,10,2))

[5, 7, 9]

>>> list(range(10,1,-1))

[10, 9, 8, 7, 6, 5, 4, 3, 2]

>>>

The range object represents a sequence of integers. By default, it will start with 0. If you

provide more parameters, it will start and end at particular points and can even skip items. In

our ﬁrst example, range(10), the sequence starts with 0 and goes up to but does not include

10. In our second example, range(5, 10) starts at 5 and goes up to but not including 10.

range(5, 10, 2) performs similarly but skips by twos (again, 10 is not included).

Strings are sequential collections of zero or more letters, numbers and other symbols. We call

these letters, numbers and other symbols characters. Literal string values are differentiated

from identiﬁers by using quotation marks (either single or double).

>>> "David"

'David'

>>> my_name = "David"

>>> my_name[3]

1.4. Review of Basic Python 13

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