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Converting Data Types
String Operations Python 2.7
Essentials
Useful String functions: Convert anything to a string:
newstring = str()
Make lowercase: "A".lower()="a"
POCKET REFERENCE GUIDE
newstring = str(100)
Make UPPERCASE : "a".upper()="A"
SANS Institute
Make Title Format: "hi world".title()="Hi World"
www.sans.org/sec573
Convert String to Integer:
Replace a substring: "123".replace('2','z')= "1z3"
http://isc.sans.edu
newint = int([,base])
Mark Baggett Twitter: @markbaggett
Count occurrences of substring:"1123".count("1")=2
All of the following assign the
Get offset of substring in string: "123".index("2")=1
variable ten the integer 10
Detect substring in string: “is” in “fish” == True
3 Methods of Python Execution
>>> ten = int(“1010”,2)
Encode "a string": "a string".encode(codec name)
>>> ten = int(“0010”)
Decode a string: "a string".decode(codec name)
Command line Execution with -c:
>>> ten = int(“000A”,16)
Example with the ROT13 codec:
# python –c [“script string”]
>>> print "RAPBQR-ZR".decode("rot13")
python –c "print 'Hello World!'"
Convert Float to Integer by dropping decimal:
ENCODE-ME
newint = int()
Python Interpreter Script Execution:
>>> print int(3.1415)
Some String encoders/decoder codec names:
# cat helloworld.py
3
Base64, bz2 , hex, rot13, uu, zip, string_escape
print "Hello World"
>>> int(3.6)
# python helloworld.py
3
Convert a string to a list (default separator=space): Hello World
newlist = astr.split()
Convert String or number to Float:
>>> print "A B C".split()
Python Interactive Shell:
afloat = float()
['A', 'B', 'C'] # python
>>> print float("1.5")
>>> print "A B C".split() >>> print "Hello World"
1.5
['A', 'B', 'C'] Hello World
>>> print float(1)
>>> print "A,B, ,C".split(",")
1.0
['A', 'B', ' ', 'C']
>>> print "WANNA BANANA?".split("AN")
Convert String Character to ASCII decimal:
['W', 'NA B', '', 'A?']
Python Command Line Options
newint = ord()
>>> print ord("A")
# python –c “script as string”
Convert a list (or other iterable object) to a string:
65
Join a list together putting string between elements. Execute a string containing a script
# python –m [module args]
“astring”.join([list])
Convert ASCII decimal to String of length 1:
>>> print "".join(['A','B','C']) Find module in path and execute as a script
newstr = chr()
ABC Example: python –m “SimpleHTTPServer”
>>> print chr(65)
>>> print ",".join(['A','B','C']) # python –i
A
A,B,C
Drop to interactive shell after script execution
SEC573 PyWars Essentials
Loops Lists & Dictionaries Misc
Create pyWars Object
List essentials: Adding Comments to code:
>>> import pyWars
#Comments begin the line with a pound sign
Create an empty list: newlist=[]
>>> game= pyWars.exercise()
Assign value at index: alist[index]= value
Defining Functions:
Access value at index alist[index]
Account Mangement
Here is a function called “add”. It accepts 2 arguments
Add item to list: alist.append(new item)
>>> game.new_acct("username","password")
num1 and num2 and returns their sum. Calling “print
Insert into list: alist.insert(at position, new item)
>>> game.login("username","password")
add(5,5)” will print “10” to the screen:
Count # of an item in list: alist.count( item )
>>> game.logout()
Delete 1 matching item: alist.remove(del item)
def add(num1, num2):
Remove item at index del alist[index]
Query a question:
#code blocks must be indented
>>> game.question()
#each space has meaning in python
Dictionary essentials:
myresult = num1 + num2
Create an empty dict: dic={} return myresult Query the data:
>>> game.data()
Initialize a non-empty dictionary:
dic = { “key1”:”value1”,”key2”:”value2”} if then else statements:
if : Submit an answer:
Assign a value: dic[“key”]=”value”
>>> game.answer(,
#code block here will execute
Determine if key exists: dic.has_key(“key”)
solverfunc(game.data()))
#when logic test 1 is True
Access value at key: dic[“key”], dic.get(“key”)
elif :
List of all keys: dic.keys()
#code block executes logic test 1 is
Logic and Math Operators
List of all values: dic.values()
#False and logic test 2 is True
List of (key,value) tuples: dic.items() else:
Math Operator Example X=7, Y=5
#code block for else has no test and
Addition X + Y 12
#executes when if an all elif are False
Looping examples:
Subtraction X - Y 2
For loop 0 thru 9: for x in range(10):
Slicing and Indexing Strings, Lists, etc
Multiplication X * Y 35
For loop 5 thru 10: for x in range(5,11):
Division X / Y 1
For each char in a string: for char in astring:
Slicing strings and lists:
Division X / float(Y) 1.4
For items in list : for x in alist:
x[start:stop:step] x=[4,8,9,3,0] x=”48930”
Exponent X ** Y 16807
For loop retrieving indexes and values in a list :
x[0] 4 ‘4’
Modulo X % Y 2
for index,value in enumerate(alist):
x[2] 9 ‘9’
Logic Operator
For keys in a dict : for x in adict.keys():
x[:3] [4,8,9] ‘489’
For items in dict : for key,value in adict.items(): Equality X == Y False
x[3:] [3,0] ‘30’
while do: Greater Than X > Y False
x[:-2] [4,8,9] ‘489’
Less Than X < Y True
x[::2] [4,9,0] ‘490’
Loop Control statements (for and while):
Less or Equal X <= Y True
x[::-1] [0,3,9,8,4] ‘03984’
Exit loop immediately break
Not Equal X !=Y or X<>Y True
len(x) 5 5
Skip rest of loop and do loop again continue
Other Logical Operators: AND, OR and NOT
sorted(x) [0,3,4,8,9] ['0', '3', '4', '8', '9']
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