python basics - cs.ucf.eduxiaoman/spring/learnpython/easypython1.pdfpython basics presented by jun...
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Python Basics
Presented by Jun Ding
Aug, 2015
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Why Python?
Easy 2 LearnCoding FastSimple Syntax…..
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Install it? Simple!(1) For Linux Users (e.g. Ubuntu)
The python is installed by default for most Linux OS.
If not, you can easily install it by using the following command:
sudo apt-get install python (Debian/Ubuntu)
sudo yum install python (ReaHat/CentOS/Fedora)
(2) Windows and Mac OS Users
Just download the python from it’s website
http://www.python.org/download/releases/2.7.6/
Double click to install it. That’s it.
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Is there any books/tutorials very helpful?
(1) OnLine tutorial
http://www.learnpython.org/
(2) Book
Dive into Python
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Where to start?Let’s try a few simple examples to show how simple
python is.
(1) Print “Hello World!”
(2) Calculate 10+26,26.2/15
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Basic Syntax-DataType
Too boring to learn the grammar?
No! you don’t have to do that. Let’s just see a few
examples. You will find there is no “learning” grammar
at all.
Data type:
int e.g. 7
float e.g. 7.1
string “I am a string”
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Basic container:
list (*) A=[1,2,3,4]
Tuple (a special case of list, immutable list)
dictionary D={‘A’:0,’C’:1,’G’:2,’T’:3}
(Example1.py)
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From the above example, we have seen :
(1) int : lengthA=6
(2) float: Element in A is float A[0]=4.0
(3) Boolean: AGB –True of False
(4) List
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Basic Syntax-ListList is almost the most important DataType in Python.
Almost, for all kinds of data, you can store them in List.
A=[4.0,6.0,7.0,9.7,1.2]
There are many important List functions, which you
need to know. We will study them in the following
example. (UseList.py)
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Basic Syntax-List
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*Things to remember*:
• A[x], get element in list A at position x
• A.append(x), append x to A list
• A.insert(p,x), insert x to A at position p
• A. index(x), get the first position of x in A, error it not found
• A.count(x), get the occurrence of x in A
• A.sort(reverse=True/False), sort list A. True/False set the
sorting order.
• A[x:y] , get the subset of list A from position x to position y.
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Basic Syntax-StringThere are lots of operations to string. We will discuss
about some important string operations.
We will also learn them from an example
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Basic Syntax-String
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Basic Syntax-String
*Things to remember*:
• A[x], get the element at position x of A
• len(A), get the length of string A
• A.upper(), get all uppercase of string A
• A.lower(), get all lowercase of string A
• A.split(), split string A with specific separator.
• .join(Asplit), join the list of strings with the separator
-> string
• A[x:y] the substring of A from x to y
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Basic Syntax-flow control
There are 3 important types of flow-control
(1) If
(2) for
(3) While
Please see example code(controlFlow.py)
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Basic Syntax-flow control
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Basic Syntax-flow control
*Things need to remember*:
(1) if-else
if (condition A):
statement A
else:
statement B
(1) For
for i in A:
statement A
(1) While
while(condition A):
statement B
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Basic Syntax- List comprehension
This is a useful technique regarding to python list
A=[1,2,3,4,5]
If we want to get the sublets of A, in which all
elements >3. How did we do this
See example code listcomprehension.py
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Basic Syntax- List comprehension
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Basic Syntax-mathBasic math in python
+,-,*,/,**,sqrt(),and etc.
See the following example code of math
(math.py)
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Basic Syntax-math
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Basic Syntax-Function
Python function is very important, it can help you to
organize your code well and improve the efficiency.
Please see the code example
(UseFunction.py)
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Basic Syntax-Function
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Basic Syntax-Function
*Things to remember*:
Please try to use function as possible as you can.
It can improve the re-usability of your code.
You don’t need to code the same function twice if it
already implemented.
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Basic Syntax-Files
Handling files is also important.
Unlike in java/c++, handling files in python is easy.
(1) read in files
(2) write files
Please see the example code in HandleFile.py
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Basic Syntax-Files
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Basic Syntax-Files
*Things to remember*:
(1) Input
f=open(“filename”,’r’)
lf=f.readlines()
f.close()
(2) Output
f=open(“filename”,’w’)
f.write(String)
f.close()
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Congrats!, you are done with
Python Basics
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Do your homework:
(1) Try toy example codes from
http://www.learnpython.org/
(2) Get familiar with the functions mentioned in this
slides
(3) In the next class, we will study on solving real
problems by using python. ( You might be asked to
write some simple code, so please be prepared).
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Questions ?