Python-List comprehension
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This document discusses list comprehensions in Python. It provides examples of using list comprehensions to generate lists based on conditions. It describes generating a list of squares of numbers from 1 to 20 and generating a list of letters from a dictionary whose values are greater than or equal to 3. It then discusses using list comprehensions to solve practice problems involving loading height data from a file, summarizing statistics, looking up heights, finding people above a certain height, and printing a report of heights.
![List Comprehension
Math World:
• Components
S = {2 · x|x ∈ N, x < 4}
• for
• if
Python World:
• else
S = [2*x for x in range(1,20) if x<4]
NCCU, Department of Computer Science
Python Programming for Non-Programmer {x} List Comprehension
Introduction](https://image.slidesharecdn.com/listcomprehension-101220192631-phpapp02/85/Python-List-comprehension-2-320.jpg)
![Case 1
• Q: Generate a list contains square of
numbers between 1 and 20.
• A:
[x**2 for x in range(1,20+1)]
NCCU, Department of Computer Science
Python Programming for Non-Programmer {x} List Comprehension
Introduction](https://image.slidesharecdn.com/listcomprehension-101220192631-phpapp02/85/Python-List-comprehension-3-320.jpg)
![Case II
• Q: Give dictionary D as following:
{‘a’:1, ‘b’:2, ‘c’:3, ‘d’:4, ‘e’:5}
Please generate the letters who has the
value which is greater than or equal 3.
• A: for x in D.keys() if D[x]>=3]
[x
[k for k,v in D.items() if v>=3]
NCCU, Department of Computer Science
Python Programming for Non-Programmer {x}
List Comprehension
Introduction](https://image.slidesharecdn.com/listcomprehension-101220192631-phpapp02/85/Python-List-comprehension-4-320.jpg)
Python-List comprehension
- 1. { x|x > 1, x ∈ N } List Comprehension - Quick Generation of List NCCU, Department of Computer Science Python Programming for Non-Programmer
- 2. List Comprehension Math World: • Components S = {2 · x|x ∈ N, x < 4} • for • if Python World: • else S = [2*x for x in range(1,20) if x<4] NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 3. Case 1 • Q: Generate a list contains square of numbers between 1 and 20. • A: [x**2 for x in range(1,20+1)] NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 4. Case II • Q: Give dictionary D as following: {‘a’:1, ‘b’:2, ‘c’:3, ‘d’:4, ‘e’:5} Please generate the letters who has the value which is greater than or equal 3. • A: for x in D.keys() if D[x]>=3] [x [k for k,v in D.items() if v>=3] NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 5. Practice • Review assignment IV • Warm up for assignment V NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 6. Practice • Q: It’s about height of people, please design a program to summarize and statistic the data in data file given in TA session. • Data file: pastie.org/1393033 • Architecture file: pastie.org/1393073 NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 7. Functions • Load from file • Summary of heights • Lookup a person’s height • Person above a height • Print height report (three in a row) NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 8. Load from file • Load data from a file into a dictionary • Key: name • Value: height • Hint: as what last assignment does NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 9. Summary the Height • Print out the following three information: - Highest height - Lowest height - Average height • Hint: try to sort the data by values, and pick up the head and the tail of the sequence. NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 10. Lookup a Height • Ask a name and query the height of it • Hint: as what last assignment does NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 11. Person Above Height • Find out who is taller than specific height • Hint: use “List Comprehension” NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 12. Print Report • Enumerate all people and their height each by each • Make output three records in row, like following: a, 152; b,180; c, 190; d, 161; e, 229; f, 191; g, 175; h, 159; • Hint: Embedded a counter to your loop NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction
- 13. That’s all, just do it. NCCU, Department of Computer Science Python Programming for Non-Programmer {x} List Comprehension Introduction