Wrap-up; Reference guide: Python concepts from module 3
Congratulations!
We accomplished a lot together.
Let's take time to quickly go through all the new concepts we covered.
We started this course by focusing on working with strings and lists.
We learned methods that work specifically with these data types.
We also learned to work with indices and extract information we need.
Next, we focused on writing algorithms.
We wrote a simple algorithm that sliced the network ID from a list of IP addresses.
Finally, we covered using regular expressions.
Regular expressions allow you to search for patterns, and this provides expanded ways to locate what you need in logs and other files.
These are complex concepts, and you're always welcome to visit the videos again whenever you like.
With these concepts, you took a big step towards being able to work with data and write the algorithms that security professionals need.
Throughout the rest of this course, you're going to get more practice with Python and what it can offer to security analysts.
Reference guide: Python concepts from module 3
Google Cybersecurity Certificate
Built-in functions
The following built-in functions are commonly used in Python.
str()
Converts the input object to a string
str(10)
Converts the integer 10 to the string "10"
len()
Returns the number of elements in an object
print(len("security"))
Returns and displays 8, the number of characters in the string "security"
String methods
The following methods can be applied to strings in Python.
.upper()
Returns a copy of the string in all uppercase letters
print("Security".upper())
Returns and displays a copy of the string "Security" as "SECURITY"
.lower()
Returns a copy of the string in all lowercase letters
print("Security".lower())
Returns and displays a copy of the string "Security" as "security"
.index()
Finds the first occurrence of the input in a string and returns its location
print("Security".index("c"))
Finds the first occurrence of the character "c" in the string "Security" and returns and displays its index of 2
List methods
The following methods can be applied to lists in Python.
.insert()
Adds an element in a specific position inside the list
username_list = ["elarson", "fgarcia", "tshah"]
username_list.insert(2,"wjaffrey")
Adds the element "wjaffrey" at index 2 to the username_list; the list becomes ["elarson", "fgarcia", "wjaffrey", "tshah"]
.remove()
Removes the first occurrence of a specific element inside a list
username_list = ["elarson", "bmoreno", "wjaffrey", "tshah"]
username_list.remove("elarson")
Removes the element "elarson" from the username_list; the list becomes ["fgarcia", "wjaffrey", "tshah"]
.append()
Adds input to the end of a list
username_list = ["bmoreno", "wjaffrey", "tshah"]
username_list.append("btang")
Adds the element "btang" to the end of the username_list; the list becomes ["fgarcia", "wjaffrey", "tshah", "btang"]
.index()
Finds the first occurrence of an element in a list and returns its index
username_list = ["bmoreno", "wjaffrey", "tshah", "btang"]
print(username_list.index("tshah"))
Finds the first occurrence of the element "tshah" in the username_list and returns and displays its index of 2
Additional syntax for working with strings and lists
The following syntax is useful when working with strings and lists.
+ (concatenation)
Combines two strings or lists together
device_id = "IT"+"nwp12"
Combines the string "IT" with the string "nwp12" and assigns the combined string of "ITnwp12" to the variable device_id
users = ["elarson", "bmoreno"] + ["tshah", "btang"]
Combines the list ["elarson", "bmoreno"] with the list ["tshah", "btang"] and assigns the combined list of ["elarson", "bmoreno", "tshah", "btang"] to the variable users
[] (bracket notation)
Uses indices to extract parts of a string or list
print("h32rb17"[0])
Extracts the character at index 0, which is ("h"), from the string "h32rb17"
print("h32rb17"[0:3])
Extracts the slice [0:3], which is ("h32"), from the string "h32rb17"; the first index in the slice (0) is included in the slice but the second index in the slice (3) is excluded
username_list = ["elarson", "fgarcia", "tshah"]
print(username_list[2])
Extracts the element at index 2, which is ("tshah"), from the username_list
Regular expressions
The following re module function and regular expression symbols are useful when searching for patterns in strings.
re.findall()
Returns a list of matches to a regular expression
import re
re.findall("a53", "a53-32c .E")
Returns a list of matches to the regular expression pattern "a53" in the string "a53-32c .E"; returns the list ["a53"]
\w
Matches with any alphanumeric character; also matches with the underscore (_)
import re
re.findall("\w", "a53-32c .E")
Returns a list of matches to the regular expression pattern "\w" in the string "a53-32c .E"; matches to any alphanumeric character and returns the list ["a", "5", "3", "3", "2", "c", "E"]
.
Matches to all characters, including symbols
import re
re.findall(".", "a53-32c .E")
Returns a list of matches to the regular expression pattern "." in the string "a53-32c .E"; matches to all characters and returns the list ["a", "5", "3", "-", "3", "2", "c", " ", ".", "E"]
\d
Matches to all single digits
import re
re.findall("\d", "a53-32c .E")
Returns a list of matches to the regular expression pattern "\d" in the string "a53-32c .E"; matches to all single digits and returns the list ["5", "3", "3", "2"]
\s
Matches to all single spaces
import re
re.findall("\d", "a53-32c .E")
Returns a list of matches to the regular expression pattern "\s" in the string "a53-32c .E"; matches to all single spaces and returns the list [" "]
\.
Matches to the period character
import re
re.findall("\.", "a53-32c .E")
Returns a list of matches to the regular expression pattern "\." in the string "a53-32c .E"; matches to all instances of the period character and returns the list ["."]
+
Represents one or more occurrences of a specific character
import re
re.findall("\w+", "a53-32c .E")
Returns a list of matches to the regular expression pattern "\w+" in the string "a53-32c .E"; matches to one or more occurrences of any alphanumeric character and returns the list ["a53", "32c", "E"]
*
Represents, zero, one or more occurrences of a specific character
import re
re.findall("\w*", "a53-32c .E")
Returns a list of matches to the regular expression pattern "\w*" in the string "a53-32c .E"; matches to one or more occurrences of any alphanumeric character and returns the list ["a53", " ", "32c", " ", " ", "E"]
{ }
Represents a specified number of occurrences of a specific character; the number is specified within the curly brackets
import re
re.findall("\w{3}", "a53-32c .E")
Returns a list of matches to the regular expression pattern "\w{3}" in the string "a53-32c .E"; matches to exactly three occurrences of any alphanumeric character and returns the list ["a53","32c"]