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--- notes:python_cheat_sheet [2026/07/22 23:04]
14.168.140.96 old revision restored (2026/06/10 13:43)
+++ notes:python_cheat_sheet [2026/07/24 15:24] (current)
47.79.201.32 old revision restored (2026/06/21 13:23)
@@ Line 1: / Line 1: @@
 ====== Python Cheat Sheet ======
-[[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]].
+===== Overview =====
-  * **python**/**python3.1** is the command-line interpreter with readline where available.
+[[http://www.python.org/ | Python]] is a dynamic object-oriented programming language with extensive standard libraries. These notes summarize the [[http://docs.python.org/3.0/tutorial/ | Python 3.0 tutorial]].
+===== The Interpreter =====
+  * **python**/**python3.0** is the command-line interpreter with readline where available.
   * python -c command runs a single command.
-  * %%>>> prompts for a line . ... prompts for a continuation of a previous line.%%
+  * sys.argv is a list of strings with the script if any in sys.argv[0]
+  * >>> prompts for a line . ... prompts for a continuation of a previous line
   * PYTHONSTARTUP can point to a file of startup commands
   * Expressions are evaluated and printed.
   * The last printed expression is assigned to _ .
 ===== Basics =====
   * Comments start with # .
-  * sys.argv is a list of strings with the script if any in sys.argv[0]
   * Variables can be assigned (using = ) without being defined but must be assigned before being used.
   * a,b = c,d does a multiple assignment.
@@ Line 24: / Line 30: @@
   * lambda x: x + n creates a small anonymous function.
   * A function should contain a triply quoted doc string at the start. This is accessible with func.__doc__ .
-  * 4 spaces per indent, no tabs. CamelCase for classes lower_case with underscores for functions.
+  * 4 spaces per indent, no tabs. CamelCasel for classes lower_case_with_underscores for functions.
 ===== Lists =====
@@ Line 41: / Line 47: @@
   * Other sequence types include tuples ( (1,2) or 1,2) and sets ({1,2} or set(1,2)).
-===== Input/Output =====
+===== Strings =====
   * 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).
@@ Line 48: / Line 54: @@
   * A string can be treated as a list of letters.
   * 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/3.0/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 =====
@@ Line 82: / Line 81: @@
   * Dictionaries are unordered sets of key value pairs e.g. { a:1, b:2} or dict([(a,1),(b,2)]) or dict(a=1,b=2)
   * Dictionary keys/values/items can be enumerated over.
-  * sorted and reversed take in lists and return new lists.
+  * sorted and reversed take in liats and return new lists.
   * enumerate takes in a list and returns a list of pairs where the first item in the pair is an integer starting with 0.
   * zip takes two or more lists with the same number of elements and creates a single list of lists with corresponding members grouped together.
@@ Line 100: / Line 99: @@
   * . is the current package, .. is the parent package etc.
-===== Error Handling =====
+===== Input/Output =====
-  * Syntax errors are parsing errors, exceptions are runtime errors.
+  * str() returns a readable representations, repr() returns a canonical representation
-  * Exceptions are class objects in the exceptions module. [[http://docs.python.org/3.1/library/exceptions.html#bltin-exceptions | List of builtin exceptions]].
+  * Strings have several formatting methods.
-  * Exception handling is supported using try..except..else..finally :<code python>
+  * //formatstring.format(tuple)// is the [[http://docs.python.org/3.0/library/string.html#formatspec | new-style printf]] equivalent. The [[http://docs.python.org/3.0/library/stdtypes.html#old-string-formatting | old-style]] was //formatstring % (tuple)// which uses C-type format strings.
-try:
+  * To open a file <code python> open('/tmp/workfile', 'w') </code>
-    result = x / y
+  * [[http://docs.python.org/3.0/library/stdtypes.html#file-objects | File methods]] include read, readline, write.
-except ZeroDivisionError:
+  * //pickle// contains load and dump methods for serializing objects. Support should be added for new object types.
-    print("division by zero!")
-except Exception as inst:
-    print(type(inst))    # the exception instance
-    print(inst.args)     # arguments stored in .args
-    print(inst)          # also prints .args
-else:
-    print("result is", result)
-finally:
-    print("executing finally clause")
-</code>
-  * 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.
-  * ''with'' can be used to automatically call the cleanup actions of an object e.g. <code python>
-with open("myfile.txt") as f:
-    for line in f:
-        print(line)
-</code>
-===== Classes =====

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