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Cheat Sheet

Python For Dummies

From Python For Dummies by Stef Maruch, Aahz Maruch

New to programming in Python? No worries. Whether you're working with string methods or built-in functions in Python, this Cheat Sheet helps you program the correct order for the operation so you achieve the correct result.

Python String Methods

The following list shows you how to perform common string methods, or actions on a string, in Python. Type the specific order to achieve the desired result.

Syntax Action
S.count(substring[, start[, end]]) Count occurrences of substring
S.decode([encoding]) Decode to Unicode using default encoding
S.encode([encoding]) Encode from Unicode using default encoding
S.endswith(suffix[, start[, end]]) True if S ends with suffix
S.find(substring [,start [,end]]) Find first occurrence of substring and return its index number; if not found, return -1
S.index(substring [,start [,end]]) Find first occurrence of substring and return its index number; if not found, raise ValueError
S.isalnum() True if S has only alphanumeric characters
S.isalpha() True if S has only alphabetic characters
S.isdigit() True if S has only digits
S.isspace() True if S has only whitespace characters
S.join(iterable) Using S as a separator, stick together the strings in iterable
S.lower() Convert S to lowercase
S.lstrip([chars]) Remove whitespace (or chars) from front (left) of S
S.replace (old, new[, count]) Replace old (a substring) with new
S.rfind(substring [,start [,end]]) Find the last (rightmost) occurrence of substring and return its index number; if not found, return -1
S.rindex(substring [,start [,end]]) Find the last (rightmost) occurrence of substring and returns its index number; if not found, raise ValueError
S.rstrip([chars]) Remove whitespace (or chars) from end (right) of S
S.split([separator [,maxsplit]]) Split S using whitespace (or separator) and return a list of substrings
S.startswith(prefix[, start[, end]]) True if S starts with prefix
S.strip([chars]) Remove characters at beginning and end of S; default is whitespace characters
S.upper() Convert S to uppercase
Note: String methods that change a string always return a copy; the original string remains unchanged.

Python's Built-In Functions

Built into the Python interpreter are a number of functions (pieces of code that carry out specific operations and return the results of those operations), including math functions other than the standard arithmetic operators. Here's a list of Python's built-in functions along with their pattern and corresponding action:

Syntax Action
abs(number) Return absolute value of number
all(iterable) Return True unless at least one element is false
any(iterable) Return False unless at least one element is true
chr(integer) Return the character with the specified ASCII value (must be between 0 and 256)
delattr(object, name), del x.y Delete the named attribute from object
dir([object]) Return the names in the current namespace or object's namespace
eval(source[, globals[, locals]]) Execute source as a Python expression
getattr(object, name[, default]) x.y Return specified attribute (name) of object, raising AttributeError if not found; optional: return default if name doesn't exist
globals() Return dict of global names in the current namespace
hasattr(object, name) True if object has the specified attribute (name)
isinstance(object, class-or-type) True if object is an instance of the specified class (or its subclasses) or type; optional: specify multiple classes or types using a tuple
issubclass(C, B) True if class C is a subclass of class B; optional: specify multiple classes using a tuple
iter(iterable) Return an iterator over iterable
len(object) Return number of items in a sequence or dict
locals() Return dictionary of local names in the current namespace
max(iterable), max(a, b, c, ...) Return largest item of iterable or argument list
min(iterable), min(a, b, c, ...) Return smallest item of iterable or argument list
ord(char) Return the ASCII value of a one-character string
range([start,] stop[, step]) Return a list of integers from 0 up to (but not including) stop
raw_input([prompt]) Return a string from standard input (usually something the user types), not including the newline character
repr(object) Return canonical string representation of object
round(number[, ndigits]) Return floating-point number rounded to nearest integer
setattr(object, name, value) x.y = v Set object's attribute to the specified value
sorted(iterable[, cmp [, key [, reverse]) Return a new sorted list; optional: cmp and key take functions as arguments; reverse=True
sum(iterable[, start=0]) Return the sum of all elements of iterable; does not work with strings
unichr(integer) Return a Unicode string corresponding to integer, which must be between 0 and 0x10ffff
xrange([start,] stop[, step]) Return an iterable that generates a range from 0 up to (but not including) stop
zip([iter1 [, iter2 [, ...]]]) Take zero or more iterables and return a list of tuples that group the items at a particular index number; the list returned is the same length as the shortest iterable
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