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====== Python Cheat Sheet ====== | ====== Python Cheat Sheet ====== | ||
- | ===== Overview ===== | + | [[http:// |
- | + | * **python**/ | |
- | [[http:// | + | |
- | * **python**/ | + | |
* python -c command runs a single command. | * python -c command runs a single command. | ||
* %%>>> | * %%>>> | ||
Line 43: | Line 41: | ||
* 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/ |
* 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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* A string can be treated as a list of letters. | * A string can be treated as a list of letters. | ||
* But strings can't be modified using slices or indexes. | * But strings can't be modified using slices or indexes. | ||
- | * [[http:// | + | * [[http:// |
+ | * // | ||
+ | * str() returns a readable representation, | ||
+ | * To open a file <code python> open('/ | ||
+ | * [[http:// | ||
+ | * //pickle// contains [[http:// | ||
+ | |||
===== Control Flow ===== | ===== Control Flow ===== | ||
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* Dictionaries are unordered sets of key value pairs e.g. { a:1, b:2} or dict([(a, | * Dictionaries are unordered sets of key value pairs e.g. { a:1, b:2} or dict([(a, | ||
* Dictionary keys/ | * Dictionary keys/ | ||
- | * sorted and reversed take in liats and return new lists. | + | * sorted and reversed take in lists 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. | * 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. | * zip takes two or more lists with the same number of elements and creates a single list of lists with corresponding members grouped together. | ||
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* . is the current package, .. is the parent package etc. | * . is the current package, .. is the parent package etc. | ||
- | ===== Input/ | + | ===== Error Handling |
- | * str() returns a readable representations, repr() returns a canonical representation | + | * Syntax errors are parsing errors, exceptions are runtime errors. |
- | * Strings have several formatting methods. | + | * Exceptions are class objects in the exceptions module. [[http:// |
- | * // | + | * Exception handling is supported using try..except..else..finally :<code python> |
- | * To open a file < | + | try: |
- | * [[http:// | + | result = x / y |
- | * //pickle// contains [[http:// | + | except ZeroDivisionError: |
+ | print(" | ||
+ | except Exception as inst: | ||
+ | print(type(inst)) | ||
+ | print(inst.args) # arguments stored in .args | ||
+ | print(inst) | ||
+ | else: | ||
+ | print(" | ||
+ | finally: | ||
+ | print(" | ||
+ | </code> | ||
+ | * Errors can be raised using '' | ||
+ | * New exception classes can be created and should derive from the Exception class. | ||
+ | * '' | ||
+ | with open(" | ||
+ | for line in f: | ||
+ | print(line) | ||
+ | </code> | ||
+ | |||
+ | ===== Classes ===== |