#Cheatsheet
###Casting Casting is the native Python way of transforming objects to other types of objects. Example:
My_number = 3
my_float = float(My_number)Casting can happen between many different types of objects
###Common whitespace characters
| Character | Meaning |
|---|---|
| \t | tab |
| \s | whitespace character. Different languages and editors may have different protocol for what is included in this designation |
| \n | newline, often used on Mac and Linux systems, may not be read properly by some PC programs |
| \r | newline, often used on PCs. May not be read properly by Mac or Linux |
###open()
Opens a file as an object in memory.
Example:
f = open('filename', 'mode')
f.open()###File Modes
| Mode | Meaning |
|---|---|
| w | write mode - can write content to this file |
| r | Read - can read from (but not write to) this file |
| a | Append - content added goes to the end of the file, as opposed to overwriting the content in the file |
| r+ | Mac and Linux - open the file for reading + writing |
| rw | Windows - open for reading + writing |
###Dictionary
Dictionaries are key : value pairs. Keys must be uniqe
Example:
my_dictionary = {}
#This initializes an empty dictionary.
my_dictionary['April'] = "Wright"
#This adds my first name as a key and my last name as a value.
my_dictionary['April']
#This calls the vlaue of my dictionary from my key, April.###Comprehensions
These are compact ways to iterate through items and populate lists.
Example:
list1 = [7, 8,9,10]
#This is a regular list declaration, as we have done before.
list2 = [x+1 for x in list1]
#This is a comprehension. list2 is declared and populated in one line.
###with
With statements can be used to execute a process, and do any necessary clean-up at the end.
Example:
with open("filename") as f:
#This opens filename and tags it to the variable f
print [line for line in f]
#this uses a list comprehension to print the file to the screen