CSE 163

Lists and Files

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Suh Young Choi�

🎶 Listening to: Max LL

💬 Before class: Happy Friday! How has your first week been?

This Time

• Lists
• Files
• Python Runtime
• Script vs Jupyter
• File Paths

Last Time

• Python Crash Course - Day 2
• Strings and String Functions
• Slicing
• Lists
• Documentation
• None

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Quick Announcements!

• Checkpoint 0 and Learning Reflection 0 released today (due Monday, 6/30 at 11:59pm)

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• Make sure to turn in Section 1 Assignment by 11:59pm today

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• Take-Home Assessment 0: Startup released today (due Thursday, 7/3 at 11:59pm)

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• Course website is online! Go check it out!

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Additional Note on CP and THA

• Optional code workspaces are given to you in Ed

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• There are no built-in tests in Ed

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• Submission checklist does not count as your submission!

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Recap: Lesson

File processing

• Line-based processing
• Token-based

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Lists

• Introduced more functions to alter lists
• Unlike strings, lists are mutable!
• The in keyword

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File paths

• Absolute vs. relative paths
• Make sure to use absolute paths in this class!

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Jupyter Notebooks (briefly)

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Files

• Process a file line by line

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• Process each word on a file in a line

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with open(file_name) as f:

lines = f.readlines()

for line in lines:

# do something with line

with open(file_name) as f:

lines = f.readlines()

for line in lines:

words = line.split()

for word in words:

# do something with word

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Strings

vs.

Lists

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s = 'hello world'

# Length

len(s) # 11

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# Indexing

s[1] # 'e'

s[len(s) - 1] # 'd'

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# Looping

for i in range(len(s)):

print(s[i])

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for c in s:

print(c)

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l = ['dog', 'says', 'woof']

# Length

len(l) # 3

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# Indexing

l[1] # 'says'

l[len(l) - 1] # 'woof'

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# Looping

for i in range(len(l)):

print(l[i])

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for word in l:

print(word)

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Advanced Lists

• List methods can modify the contents of the list (e.g. append)
• Can use the in keyword to see if a list contains a value

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words = ['I', 'love', 'dogs']

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if 'dogs' in words:

print('Found it')

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if 'cats' not in words:

print('Not there')

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• Other functions we introduced (with the exception of .index()) will modify the list data structure!

Group Work:

Best Practices

When you first working with this group:

• Introduce yourself!
• If possible, angle one of your screens so that everyone can discuss together

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Tips:

• Starts with making sure everyone agrees to work on the same problem
• Make sure everyone gets a chance to contribute!
• Ask if everyone agrees and periodically ask each other questions!
• Call TAs over for help if you need any!

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Before Next Time

• CP + LR 0 due Monday
• Complete Lesson 4
• Get started on TH0!

Next Time

• More Data Structures
• Tuples
• Sets
• Dictionaries

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