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notes:python_cheat_sheet [2009/12/18 17:56]
smthng 		notes:python_cheat_sheet [2009/12/18 18:06] (current)
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 ====== Python Cheat Sheet ====== ====== Python Cheat Sheet ======
- 
-===== Overview ===== 
  
 [[http://www.python.org/ | Python]] is a dynamic object-oriented programming language with extensive standard libraries. These notes summarize the [[http://docs.python.org/3.1/tutorial/ | Python 3.1 tutorial]]. [[http://www.python.org/ | Python]] is a dynamic object-oriented programming language with extensive standard libraries. These notes summarize the [[http://docs.python.org/3.1/tutorial/ | Python 3.1 tutorial]].
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   * Other sequence types include tuples ( (1,2) or 1,2) and sets ({1,2} or set(1,2)).   * Other sequence types include tuples ( (1,2) or 1,2) and sets ({1,2} or set(1,2)).
  
-===== Strings =====+===== Input/Output =====
   * Strings can be enclosed with double or single-quotes.   * Strings can be enclosed with double or single-quotes.
   * \ in a string by itself goes to the next line but does not insert a newline (\n does).   * \ in a string by itself goes to the next line but does not insert a newline (\n does).
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   * But strings can't be modified using slices or indexes.   * But strings can't be modified using slices or indexes.
   * [[http://docs.python.org/3.1/library/stdtypes.html#string-methods | String methods]] include strip, format, capitalize etc.   * [[http://docs.python.org/3.1/library/stdtypes.html#string-methods | String methods]] include strip, format, capitalize etc.
 +  * //formatstring.format(tuple)// is the [[http://docs.python.org/3.1/library/string.html#formatspec | new-style printf]] equivalent. The [[http://docs.python.org/3.1/library/stdtypes.html#old-string-formatting | old-style]] was //formatstring % (tuple)// which uses C-type format strings.
 +  * str() returns a readable representation, repr() returns a canonical representation of any object.
 +  * To open a file <code python> open('/tmp/workfile', 'w') </code>
 +  * [[http://docs.python.org/3.1/library/stdtypes.html#file-objects | File methods]] include read, readline, write.
 +  * //pickle// contains [[http://docs.python.org/3.1/library/pickle.html | load and dump methods]] for serializing objects. Support should be added for new object types.
 +
 +
  
 ===== Control Flow ===== ===== Control Flow =====
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   * Packages can be used to group modules. Packages should be in a named directory with an __init__.py file optionally containing initialization code. E.g. import sound.effects.echo .   * Packages can be used to group modules. Packages should be in a named directory with an __init__.py file optionally containing initialization code. E.g. import sound.effects.echo .
   * . is the current package, .. is the parent package etc.   * . is the current package, .. is the parent package etc.
- 
-===== Input/Output ===== 
- 
-  * str() returns a readable representations, repr() returns a canonical representation 
-  * Strings have several formatting methods.  
-  * //formatstring.format(tuple)// is the [[http://docs.python.org/3.1/library/string.html#formatspec | new-style printf]] equivalent. The [[http://docs.python.org/3.1/library/stdtypes.html#old-string-formatting | old-style]] was //formatstring % (tuple)// which uses C-type format strings. 
-  * To open a file <code python> open('/tmp/workfile', 'w') </code> 
-  * [[http://docs.python.org/3.1/library/stdtypes.html#file-objects | File methods]] include read, readline, write. 
-  * //pickle// contains [[http://docs.python.org/3.1/library/pickle.html | load and dump methods]] for serializing objects. Support should be added for new object types. 
  
 ===== Error Handling ===== ===== Error Handling =====
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   * Syntax errors are parsing errors, exceptions are runtime errors.   * Syntax errors are parsing errors, exceptions are runtime errors.
   * Exceptions are class objects in the exceptions module. [[http://docs.python.org/3.1/library/exceptions.html#bltin-exceptions | List of builtin exceptions]].   * Exceptions are class objects in the exceptions module. [[http://docs.python.org/3.1/library/exceptions.html#bltin-exceptions | List of builtin exceptions]].
-  * Exception handling is supported using try..except..else..finally : +  * Exception handling is supported using try..except..else..finally :<code python>
-<code python>+
 try: try:
-   result = x / y+    result = x / y
 except ZeroDivisionError: except ZeroDivisionError:
-   print("division by zero!")+    print("division by zero!")
 except Exception as inst: except Exception as inst:
-   print(type(inst))    # the exception instance +    print(type(inst))    # the exception instance 
-   print(inst.args)     # arguments stored in .args +    print(inst.args)     # arguments stored in .args 
-   print(inst)          # also prints .args+    print(inst)          # also prints .args
 else: else:
-   print("result is", result)+    print("result is", result)
 finally: finally:
-   print("executing finally clause")+    print("executing finally clause")
 </code> </code>
   * Errors can be raised using ''raise Exception('mine')'' or just ''raise'' in an exception handler.   * Errors can be raised using ''raise Exception('mine')'' or just ''raise'' in an exception handler.
   * New exception classes can be created and should derive from the Exception class.   * New exception classes can be created and should derive from the Exception class.
-  * ''with'' can be used to automatically call the cleanup actions of an object e.g. +  * ''with'' can be used to automatically call the cleanup actions of an object e.g. <code python>
-<code python>+
 with open("myfile.txt") as f: with open("myfile.txt") as f:
     for line in f:     for line in f:
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 </code> </code>
  
 +===== Classes =====
 
 
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