It seems that route 22 does not have.24 hours service. If you try the Exercise 1.4 when the service is not in operation nothing gets printed:

>>> u = urllib.request.urlopen('http://ctabustracker.com/bustime/map/getStopPredictions.jsp?stop=14791&route=22')
>>> doc = parse(u)
>>> for pt in doc.findall('.//pt'):
...     print(pt.text)                                                          ... 
>>> 

This might be worrying for someone who is new to Python. After viewing the xml via a browser, I was able to work out why there was no output.

>>> for pt in doc.findall('.//noPredictionMessage'):                            ...     print(pt.text)
... 
No arrival times

I did manage to get an arrival time using route 5 & stop 12023 but that seems to be a night only service. (I have never visited Chicago).

>>> u = urllib.request.urlopen('http://ctabustracker.com/bustime/map/getStopPredictions.jsp?stop=12023&route=5')
>>> doc = parse(u)
>>> for pt in doc.findall('.//pt'):                                             ...     print(pt.text)                                                          ... 
APPROACHING
24 MIN

Perhaps a word of warning could be given along the lines of

"If you try this in the middle of the night or live overseas, there may be no buses running on route 22. If you don't see a list of pending arrivals, try to check for bus route 5 at stop 12023."

https://dabeaz-course.github.io/practical-python/Notes/01_Introduction/04_Strings.html

a = 'Hello world'
...
f = a[3:8]    # 'lowo'  # should be 'lo wo'

From the description it is not clear if the extra payment start and/or end month should be included in the range. The exercise asks for "4 years starting in year 5", the code shows an exclusive range [60, 108], but the solution uses an inclusive range with ">=" and "<=" which results in 49 months.

What a great resource
Minor typo here
Notes/01_Introduction/03_Numbers.md#converting-numbers

>>> b = '3.14159' # It also works with strings containing numbers
>>> float(b)
3.15159

3.15159

I mean add https://dabeaz-course.github.io/practical-python/ here:

# mortgage.py

principal = 500000.0
rate = 0.05
payment = 2684.11
total_paid = 0.0

while principal > 0:
    principal = principal * (1+rate/12) - payment
    total_paid = total_paid + payment

print('Total paid', total_paid)

Enter this program and run it. I get an answer of 966279.5999999957. Not 966,279.6.

I can get an anwer of 966,279.6 by following:

# Exercise 1.7


principal = 500000.0
rate = 0.05
payment = 2684.11
total_paid = 0.0

while principal > 0:
    principal = principal * (1+rate/12) - payment
    total_paid = total_paid + payment

print('Total paid', round(total_paid, 1))

In "5.2 Classes and Encapsulation" under "Decorator Syntax" you have
*decoration”

It would be nice if the course pages had a return link to the welcome page (https://dabeaz-course.github.io/practical-python/) that was a bit more obvious than the GitHub fork link at the bottom of the page.

The Welcome page includes some resource links (like this Issue Tracker) that should be a little easier to get to. One possible solution would be to make the 'Practical Python Programming' title on each instruction page an active link back to the welcome.

Just a thought, feel free to modify/discard....

Under Macos and ubuntu '\N{FORALL}' gives a unicode error

>>> d = '\N{FORALL}'
  File "<stdin>", line 1
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 0-9: unknown Unicode character name

but '\N{FOR ALL}' works

>>> d = '\N{FOR ALL}'
>>> d
'∀'

on this page https://github.com/dabeaz-course/practical-python/blob/master/Notes/01_Introduction/00_Overview.md

the first link https://github.com/dabeaz-course/practical-python/blob/master/Notes/01_Introduction/01_Python is giving 404

In the last line, instead of pointing to contents.md, it is pointing to contents.html.
https://github.com/dabeaz-course/practical-python/blob/master/Notes/InstructorNotes.md

Warning: It is never possible to paste more than one Python command (statements that appear after >>>) to the basic Python shell at a time. You have to paste each command one at a time.

This is false, at least on FreeBSD with xfce4-terminal. I've been using Python for 6 years and can't remember this ever being true.

In "5.2 Classes and Encapsulation" in subsection "Managed Attributes" you have:

class Stock:
def init(self, name, shares, price):
self.name = name self.set_shares(shares) self.price = price

I imagine those were intended to be on separate lines.

In https://dabeaz-course.github.io/practical-python/Notes/02_Working_with_data/07_Objects.html

"With great power come responsibility" should be "With great power comes responsibility".
I might not be correct, English is not my first language.

In paragraph following "Exercises" "...from previous sctions." should be "...from previous sections.

Hi Dave,

just working through the Practical Python course in preparation for the Advanced Python Course in July.

In the chapter 1.6 right at the start you are showing an example of how to read a file:

f = open('foo.txt', 'rt') # Open for reading (text)

The file doesn't exist in the Work folder so an exception occurs that might be confusing for people.

I think there should be a example file. Or even better reverse the order of reading and writing to a file and let the people first write some text to a file "foo.txt" and let them read it in again afterwards.

Not be confused with the C-style formatting.

I think it would be helpful to let the reader know that you can do this:

>>> a_third = 1/3
>>> f'{a_third:.2%}' 
'33.33%'

https://dabeaz-course.github.io/practical-python/Notes/07_Advanced_Topics/01_Variable_arguments.html

"Dictionaries can also be expaded into keyword arguments."

expaded => expanded

Nachiket

https://dabeaz-course.github.io/practical-python/Notes/01_Introduction/03_Numbers.html

Reads:
a === 6.3

It should probably be a == 6.3

Do you want slist here? It's a little confusing.

s.join(slist) # Joins lists using s as delimiter

Hi Dave,
I've just found this tiny bug in the example below. As mentioned on more than one occasion it is assumed that our working directory is ./Work/ therefore the code below will raise a FileNotFoundError because of the missing path.

Exercise 2.5: List of Dictionaries
Take the function you wrote in Exercise 2.4 and modify to represent each stock in the portfolio with a dictionary instead of a tuple. In this dictionary use the field names of "name", "shares", and "price" to represent the different columns in the input file.

Experiment with this new function in the same manner as you did in Exercise 2.4.

>>> portfolio = read_portfolio('portfolio.csv')

results in:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "report.py", line 24, in read_portfolio
    with open(filename, 'rt') as f:
FileNotFoundError: [Errno 2] No such file or directory: 'portfolio.csv'

To fix this add the correct path to the file:

>> portfolio = read_portfolio('Data/portfolio.csv')

https://dabeaz-course.github.io/practical-python/Notes/01_Introduction/02_Hello_world#types

Reads:

height = 442           # An integer
height = 442           # Floating point

That second value should probably be 442..

On https://dabeaz-course.github.io/practical-python/Notes/02_Working_with_data/02_Containers.html under "Sets" section you have: # Alternative sintax

Hello dabeaz,

when I took the course I had to modify the marked a part of the script to make it work (Chapter 3.1, last script at the bottom):

'prices.csv' --> 'Data/prices.csv'

Just a minor improvement to your awesome course.

Cheers,
vraez

This is incredibly minor, but in 4.1, there's an example class with a move method.

def move(self, dx, dy):
    self.dx += dx
    self.dy += dy

Since there is no dx or dy attributes and you wouldn't add a change in x to a change in x, I think this was supposed to be:

def move(self, dx, dy):
    self.x += dx
    self.y += dy

In "Exercise 2.16: Using the zip() function" the sentence near the end of the exercise "Modify the report.py program you wrote in Section 2.3 that it uses..." would read better as "Modify the report.py program you wrote in Section 2.3 so that it uses..."

In list comprehensions section under "Historical Digression": "List comprehension come from..." should be "List comprehensions come..."

In section 1.2 the following example is used for Looping and Indentation:

while num_bills * bill_thickness < sears_height:
    print(day, num_bills, num_bills * bill_thickness)
    day = day + 1
    num_bills = num_bills * 2

print('Number of days', days)

If the intention is to sample a portion of the previously shown solution, then the last line should say print('Number of days', day) to make it consistent.

Might be better as "continuing a statement".

... is the interpreter prompt for continuing a statements.

https://dabeaz-course.github.io/practical-python/Notes/03_Program_organization/05_Main_module.html

s/inclosed/enclosed

https://dabeaz-course.github.io/practical-python/Notes/01_Introduction/06_Files.html

>>> with open('Data/portfolio.csv', 'rt') as f:
    for line in f:
        print(line, end='')

name,shares,price
"AA",100,32.20
"IBM",50,91.10
...
>>>

https://github.com/dabeaz-course/practical-python/blob/master/Notes/05_Object_model/01_Dicts_revisited.md#method-resolution-order-or-mro

... called the Method Resolutin Order. The find an attribute, Python walks the MRO in order...

\Notes\02_Working_with_data\02_Containers.md

Error after code runs:

records = []  # Initial empty list

with open('Data/portfolio.csv', 'rt') as f:
    for line in f:
        row = line.split(',')
        records.append((row[0], int(row[1])), float(row[2]))

TypeError Traceback (most recent call last)
in
2
3 with open('Work/Data/portfolio.csv', 'rt') as f:
----> 4 for line in f[1:]:
5 row = line.split(',')
6 records.append((row[0], int(row[1])), float(row[2]))

TypeError: '_io.TextIOWrapper' object is not subscriptable

Wrong:

columns = ['name', 'shares', 'price']
values = ['GOOG', 100, 490.1 ]
pairs = zip(a, b)
# ('name','GOOG'), ('shares',100), ('price',490.1)

Correct:

columns = ['name', 'shares', 'price']
values = ['GOOG', 100, 490.1 ]
pairs = zip(columns, values)
# ('name','GOOG'), ('shares',100), ('price',490.1)

Hi

thanks for offering this course online. i've learned a ton!

on https://github.com/dabeaz-course/practical-python/blob/main/Notes/07_Advanced_Topics/02_Anonymous_function.md

this example:

def stock_name(s):
    return s['name']

portfolio.sort(key=stock_name)

can also be implemented using itemgetter:

from operator import itemgetter
portfolio.sort(key=itemgetter('name'))

see https://docs.python.org/3/howto/sorting.html#operator-module-functions
and https://docs.python.org/3/library/operator.html#operator.itemgetter

i know it kinda defeats the purpose of what you're trying to show, but it's an alternative to keep you from writing one-liners.

maybe include both?

Hi! This line from Section 1.2, Hello World about underscores bothered me a bit:

This is only true in the interactive mode. You never use _ in a program.

Is the latter part safe to say? Since the _ character can be used as a throwaway, right? Like if I want a list to contain 5 boolean values, I can do:

tracker = [True for _ in range(5)]

Maybe it can be worded as, "the underscore has a different purpose in non-interactive mode." Apologies if this is amended later on and I just haven't gotten to that part.

That aside, congratulations on this book. Loving it so far! Apologies too if I'm using GitHub incorrectly -- I'm kinda new to this.

"Sometimes the () are ommitted in the syntax."
https://dabeaz-course.github.io/practical-python/Notes/02_Working_with_data/01_Datatypes.html

The third bullet point of this section is incorrect. Lambdas may contain if/else.

For example:

In [1]: f=lambda x: "Negative" if x<0 else "Positive"

In [2]: f(1)
Out[2]: 'Positive'

In [3]: f(-11)
Out[3]: 'Negative'

In section 3.4, exercises go from 3.12 line 295 to 3.14 line 319.
Is that superstition?
=)

Anchor on GitHub.com page

The home page for the course, on GitHub.com, has the anchor Take me to the Course Already! and the following text:

Ok, ok. Point your browser HERE!

Where HERE links to the Contents.md page (part of the "blob" directory tree).

However, the Home link at the bottom of that page is generating a 404 Page Not Found error as it is not returning to the correct point in the "blob" directory tree.

The Markdown code for the link is:

[Home](..)

Perhaps it should be the following?

[Home](..\..)

Link to https://dabeaz-course.github.io/

I found the link to this GitHub repo on Hacker News. However, it was only in looking at Issue #1 that I realized that the repo is mirrored at https://dabeaz-course.github.io/practical-python/.

There is a link from the GitHub.io page to the GitHub.com repo, but there is no link, that I can see, from the GitHub repo going in the opposite direction. Did I miss something, perhaps?

The Contents page on GitHub.io has the correct Home link. I do not know how the repo and the GitHub.io pages are related, so I'm not sure if the issue mentioned above can be corrected without causing some negative impact.

Just some minor typos I found:

1. Replace "a collection of names values" with "a collection of named values"
2. Replace "A attribute search process" with "An attribute search process"
3. In the code snippet 'Dicts and Objects', replace {'name' : 'GOOG','shares' : 100, 'price': 490.1 } with {'name' : 'GOOG', 'shares' : 100, 'price': 490.1 } (additional space).

Thanks, great work!

In exercise 1.28 you're looking at a gzipped file of the same portfolio data file from the previous exercises. One can't just substitute in the gzip with command, though, since now you'll get byte strings back. I think it's worth adding a sentence clarifying this: IMO it's a bit unexpected for the reader since the compressed content is still a text file (and more reinforcement of the fact that byte strings and regular strings are different can only be a good thing.)

">>> lines = ['name,shares,price', 'AA,34.23,100',..." should be ">>> lines = ['name,shares,price', 'AA,100,34.23',..."

Notes/02_Working_with_data/01_Datatypes.md has a typo for the price value in the third code block of Exercise 2.2. It says the price is 75 when it should be 32.2, as the shares value was updated to 75, not the price value.

Diff:
@@ -338,7 +338,7 @@ above. Change the number of shares to 75.

>>> d['shares'] = 75
>>> d
-{'name': 'AA', 'shares': 75, 'price': 75}
+{'name': 'AA', 'shares': 75, 'price': 32.2}
>>>

Right here at:

OR
def bar(x)
statements

You need a colong after "bar(x)"

Chapter: https://dabeaz-course.github.io/practical-python/Notes/01_Introduction/02_Hello_world.html

At the end of section on Interactive Mode, it's stated about the underscore that "this is only true in the interactive mode. You never use _ in a program."

Perhaps the last sentence could be clarified to mean that underscores are not used to store the "previous values" (whatever that may mean in the context of programs), since _ may be used as a dummy variable.

Hi, @dabeaz or anyone there:

As a beginner of Python, I used Jupyter Notebook a lot and so LOVE it.

It's my pleasure to trans all markdown file of this repo to Jupyter Notebook file .ipynb.

but I am not sure:

Is it usefull for anyone else?
Will @dabeaz need it if i pull a Pull Request?

going back to the content to navigate between chapters is a bit tedious. It would be nice to have a "next" link somewhere to progress through the chapters.

Section 7.2 says No statements like if, while, etc. in lambda functions. While it's true that they don't handle full if-elif-else statements, it's possible (and often handy) to use ternary operators.