Show Menu
Cheatography

Learn Python the Hard Way - Symbol Review Cheat Sheet (DRAFT) by

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Keywords

Keyword
Descri­ption
Example
and
Logical and
True and False == False
as
Part of the with-as statement
with X as Y: pass
assert
Assert that something is true.
`assert False, "­Err­or!­"
break
Stop this loop right now.
while True: break
class
Define a class.
class Person­(ob­ject)
continue
Don't process more of the loop, do it again.
while True: continue
def
Define a function.
def X(): pass
del
Delete from dictio­nary.
del X[Y]
elif
Else if
if: X; elif: Y; else: J
else
Else condition
if: X; elif: Y; else: J
except
If an exception happens, do this.`
except ValueE­rror, e: print e
exec
Run a string as Python
exec 'print "­hel­lo"'
finally
Exceptions or not, finally do this no matter what.
finally: pass
for
Loop over a collection of things.
for X in Y: pass
from
Importing specific parts of a module.
from x import y`
global
Declares a global variable
global X
if
If condition
if: X; elif: Y; else: J
import
Import a module into this one to use.
import os
in
Part of for-loops. Also a test of X in Y.
for X in Y: pass also 1 in [1] == True
is
Like == to test equality
1 is 1 == True
lambda
Create a short anonymous function
s = lambda y: y ** y; s(3)
not
Logical not
not True == False
or
Logical or
True or False == True
pass
This block is empty.
def empty(): pass
print
Print this string.
print 'this string'
raise
Raise an exception when things go wrong.
raise ValueE­rro­r("N­o")
return
Exit the function with a return value.
def X(): return Y
try
Try this block, and if exception, go to except.
try: pass
while
While loop
while X: pass
with
With an expression as a variable do.
with X as Y: pass
yield
Pause here and return to caller.
def x(): yield Y; X().next()
 

Data Types

Type
Descri­ption
Example
True
True boolean value
True or False == True
False
False boolean value.
False and True == False
None
Represents "­not­hin­g" or "no value".
x = None
strings
Stores textual info
x = "­hel­lo"
numbers
Stores integers
i = 100
floats
Stores decimals
i = 10.389
lists
Stores a list of things
j = [1,2,3,4]
dicts
Stores a key=value mapping of things
e = {'x': 1, 'y': 2}

String Formats

Escape
Descri­ption
Example
%d
Decimal int
"­%d" % 45 == '45'
%o
Octal number
`%o % 1000 == '1750'
%u
Unsigned decimal
"­%u" % -1000 == '-1000'
%x
Hexade­cimal lowercase
"­%x" % 1000 == '3e8'
%X
Hexade­cimal uppercase.
"­%X" % 1000 == '3E8'
%e
Expone­ntial notation, lowercase 'e'.
"­%e" % 1000 == '1.000­000­e+03'
%E
Expone­ntial notation, uppercase 'E'.
"­%E" % 1000 == '1.000­000­E+03'
%f
Floating point real number.
"­%f" % 10.34 == '10.34­0000'
%F
Same as %f.
"­%F" % 10.34 == '10.34­0000'
%g
Either %f or %e, whichever is shorter.`
"­%g" % 10.34 == '10.34'
%G
Same as %g but uppercase.
"­%G" % 10.34 == '10.34'
%c
Character format.
"­%c" % 34 == '"'
%r
Repr format (debugging format).
"­%r" % int == "­<type 'int'>­"
%s
String format.
"%s there" % 'hi' == 'hi there'
%%
A percent sign.
"­%g%­%" % 10.34 == '10.34%'
 

String Escape Sequences

\\
Backslash
\'
Single­-quote
\''
Double­-quote
\a
Bell
\b
Backspace
\f
Formfeed
\n
Newline
\r
Carriage
\t
Tab
\v
Vertical tab