External Resources:

Copy Paste

Copying Lines:

on the line that you want to duplicate
yyp

Copy a Block:

v (for visual mode)
direction arrows to highlight
y (to copy)
i (insert mode) move to the desired area
esc
p

Delete

Deleting a Line:

On the line that you want to delete
dd

Deleting everything below the cursor:

dG

Deleting everything above the cursor:

dH

Deleting 10 Lines below the cursor:

10dd

Delete the first 4 characters of every line:

:%s/^.\{0,4\}//

eg.

>>> class HashTable:
...     def __init__(self):
...         self.size = 256
...         self.slots = [None for i in range(self.size)]
...         self.count = 0

after:

class HashTable:
    def __init__(self):
        self.size = 256
        self.slots = [None for i in range(self.size)]
        self.count = 0

Replace Characters:

Norm Function: Find/Replace

The dataset:

123. 123
233. 123

Apply:

:%norm f.C,

Result:

123,
233,

Commenting Lines:

shift + v
move down until the line you want to comment out
shift + I
Enter the character (#)
Esc

Search and Replace (replace true with false):

:%s/true/false/
press enter