Python-List comprehension

{ x|x > 1, x ∈ N }
List Comprehension - Quick Generation of List

NCCU, Department of Computer Science
Python Programming for Non-Programmer

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]

Python Programming for Non-Programmer {x} List Comprehension
Introduction

Case 1

• Q: Generate a list contains square of
numbers between 1 and 20.
• A:
[x**2 for x in range(1,20+1)]

Introduction

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]

Python Programming for Non-Programmer {x}
List Comprehension
Introduction

Practice

• Review assignment IV
• Warm up for assignment V

List Comprehension
Introduction

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
Introduction

Functions

• Load from ﬁle
• Summary of heights
• Lookup a person’s height
• Person above a height
• Print height report (three in a row)
Introduction

Load from ﬁle

• Load data from a ﬁle into a dictionary
• Key: name
• Value: height
• Hint: as what last assignment does

Introduction

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.

Introduction

Lookup a Height

• Ask a name and query the height of it
• Hint: as what last assignment does

Introduction

Person Above Height

• Find out who is taller than speciﬁc height
• Hint: use “List Comprehension”

Introduction

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
List Comprehension
Introduction

That’s all, just do it.

List Comprehension
Introduction

Python-List comprehension

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