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课程简介

Python for Everybody 零基础程序设计（Python 入门）

• This course aims to teach everyone the basics of programming computers using Python. 本课程旨在向所有人传授使用 Python 进行计算机编程的基础知识。
• We cover the basics of how one constructs a program from a series of simple instructions in Python. 我们介绍了如何通过 Python 中的一系列简单指令构建程序的基础知识。
• The course has no pre-requisites and avoids all but the simplest mathematics. Anyone with moderate computer experience should be able to master the materials in this course. 该课程没有任何先决条件，除了最简单的数学之外，避免了所有内容。任何具有中等计算机经验的人都应该能够掌握本课程中的材料。
• This course will cover Chapters 1-5 of the textbook “Python for Everybody”. Once a student completes this course, they will be ready to take more advanced programming courses. 本课程将涵盖《Python for Everyday》教科书的第 1-5 章。学生完成本课程后，他们将准备好学习更高级的编程课程。
• This course covers Python 3.

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coursera

Python for Everybody 零基础程序设计（Python 入门）

Charles Russell Severance
Clinical Professor

个人主页
Twitter

University of Michigan

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课程资源

coursera原版课程视频
coursera原版视频-中英文精校字幕-B站
Dr. Chuck官方翻录版视频-机器翻译字幕-B站

PY4E-课程配套练习
Dr. Chuck Online - 系列课程开源官网

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Quiz 9: Dictionaries

The dictionary data structures allows us to store multiple values in an object and look up the values by their key.

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单选题（1-11）

1. How are Python dictionaries different from Python lists?

• Python dictionaries are a collection and lists are not a collection
• Python lists can store strings and dictionaries can only store words
• Python lists store multiple values and dictionaries store a single value
• Python lists maintain order and dictionaries do not maintain order

2. How are Python dictionaries different from Python lists?

• Python lists are indexed using integers and dictionaries can use strings as indexes
• Python lists store multiple values and dictionaries store a single value
• Python dictionaries are a collection and lists are not a collection
• Python lists can store strings and dictionaries can only store words

3. What is a term commonly used to describe the Python dictionary feature in other programming languages?

• Sequences
• Lambdas
• Closures
• Associative arrays

4. What would the following Python code print out?

stuff = dict()
print(stuff['candy'])

• candy
• 0
• The program would fail with a traceback
• -1

5. What would the following Python code print out?

 stuff = dict()
 print(stuff.get('candy',-1))

• The program would fail with a traceback
• ‘candy’
• -1
• 0

6. (T/F) When you add items to a dictionary they remain in the order in which you added them.

• True
• False

7. What is a common use of Python dictionaries in a program?

• Building a histogram counting the occurrences of various strings in a file
• Sorting a list of names into alphabetical order
• Splitting a line of input into words using a space as a delimiter
• Computing an average of a set of numbers

8. Which of the following lines of Python is equivalent to the following sequence of statements assuming that counts is a dictionary?

if key in counts:
    counts[key] = counts[key] + 1
else:
    counts[key] = 1

• counts[key] = (counts[key] * 1) + 1
• counts[key] = counts.get(key,0) + 1
• counts[key] = key + 1
• counts[key] = counts.get(key,-1) + 1
• counts[key] = (key in counts) + 1

9. In the following Python, what does the for loop iterate through?

x = dict()
...
for y in x :
     ...

• It loops through the keys in the dictionary
• It loops through the values in the dictionary
• It loops through the integers in the range from zero through the length of the dictionary
• It loops through all of the dictionaries in the program

10. Which method in a dictionary object gives you a list of the values in the dictionary?

• keys()
• items()
• each()
• values()
• all()

11. What is the purpose of the second parameter of the get() method for Python dictionaries?

• The value to retrieve
• To provide a default value if the key is not found
• The key to retrieve
• An alternate key to use if the first key cannot be found

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编程题

Exercise 9.4

题目：
Write a program to read through the mbox-short.txt and figure out who has sent the greatest number of mail messages. The program looks for 'From ’ lines and takes the second word of those lines as the person who sent the mail.
The program creates a Python dictionary that maps the sender’s mail address to a count of the number of times they appear in the file.
After the dictionary is produced, the program reads through the dictionary using a maximum loop to find the most prolific committer.

[Desired Output]
cwen@iupui.edu 5

解题代码：

name = input("Enter file:")
if len(name) < 1:
   name = "mbox-short.txt"
handle = open(name)

d = dict()
for line in handle :
   ls = line.split()
   if line.startswith('From') and len(ls) == 7 :
       d[ls[1]] = d.get(ls[1], 0) + 1
       
bk = None
bv = None
for k,v in d.items() :
   if bv is None or v > bv :
       bv = v
       bk = k

print(bk, bv)