Last change
on this file since 1910 was 1757, checked in by Kana Sugimoto, 14 years ago |
New Development: Yes
JIRA Issue: Yes (CAS-2211)
Ready for Test: Yes
Interface Changes: Yes
What Interface Changed: ASAP 3.0.0 interface changes
Test Programs:
Put in Release Notes: Yes
Module(s): all the CASA sd tools and tasks are affected.
Description: Merged ATNF-ASAP 3.0.0 developments to CASA (alma) branch.
Note you also need to update casa/code/atnf.
|
File size:
1.9 KB
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[1636] | 1 | ====================
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| 2 | Python in 20 minutes
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| 3 | ====================
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| 4 |
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| 5 | .. sectionauthor:: Malte Marquarding
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| 6 |
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| 7 | **Main goal:** To get a basic understanding of the python programming language
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| 8 |
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| 9 |
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| 10 | This is a very quick introduction to the python programming language to get started with ASAP,
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| 11 | which behaves just like any other python module you can find.
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| 12 | It introduces basic programming concepts.
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| 13 |
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| 14 |
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| 15 | Variables
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| 16 | =========
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| 17 |
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| 18 | A variable is just an alias/handle to a value. The value can be anything understood by python
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| 19 |
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| 20 | Example::
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| 21 |
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| 22 | # an integer
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| 23 | x = 1
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| 24 | # a string
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| 25 | y = 'Hello World!'
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| 26 | # a boolean
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| 27 | z = True
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| 28 | # list of ...
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| 29 | a = [0, 1, 2]
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| 30 | b = ['a', 'b']
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| 31 |
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| 32 |
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| 33 | Syntax
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| 34 | ======
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| 35 |
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| 36 | Python uses **identation** to define blocks, where other proogramming language often use
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| 37 | curly brackets, e.g.:
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| 38 |
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| 39 | in *c*:
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| 40 |
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| 41 | .. code-block:: c
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| 42 |
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| 43 | while (i<10) {
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| 44 | j += il
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| 45 | }
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| 46 | // block ends
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| 47 |
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| 48 | in *python*:
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| 49 |
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| 50 | .. code-block:: python
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| 51 |
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| 52 | while i<10:
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| 53 | j += 10
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| 54 | # block ends
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| 55 |
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| 56 |
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| 57 | Functions
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| 58 | =========
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| 59 |
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| 60 | When you need to repeat common behaviour you are better of defining a function, just like it would be
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| 61 | in mathematics. A function can return something ot do no return anything but doing something implictly.
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| 62 |
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| 63 | Examples::
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| 64 |
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| 65 | def squared(x):
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| 66 | return x*x
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| 67 |
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| 68 | result = squared(2)
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| 69 | print result
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| 70 |
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| 71 | def prefix_print(value):
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| 72 | print 'My value:', value
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| 73 |
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| 74 | prefix_print('Hello')
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| 75 |
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| 76 | Statements
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| 77 | ==========
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| 78 |
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| 79 | Often you find you will want to do something conditionally.
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| 80 | For this you can use `if` statements.
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| 81 |
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| 82 | Example::
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| 83 |
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| 84 | a = 1
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| 85 | if a == 1:
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| 86 | print 'Match'
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| 87 | else:
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| 88 |
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| 89 | print 'No match'
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| 90 |
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| 91 | To apply a function to a range of values you can use `for` or `while`
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| 92 |
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| 93 | Example::
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| 94 |
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| 95 | i = 0
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| 96 | while i < 10:
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| 97 | print i
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| 98 | i +=1
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| 99 |
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| 100 | for i in [0, 1, 2]:
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| 101 | print i
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| 102 |
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| 103 |
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| 104 | Objects
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| 105 | =======
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| 106 |
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| 107 | Objects are basically values with certain attributes, which are specific to that type of the object.
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| 108 | For example strings in python have attribute functions which can perform operations on the string::
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| 109 |
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| 110 | x = 'Test me'
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| 111 | print x.upper()
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