Tabs and spaces in python

Spaces are not treated as equivalent to tab. A line indented with a tab is at a different indentation from a line indented with 1, 2, 4 or 8 spaces.

Proof by counter-example [erroneous, or, at best, limited - tab != 4 spaces]:

x = 1
if x == 1:
^Iprint "fff\n"
    print "yyy\n"

The '^I' shows a TAB. When run through Python 2.5, I get the error:

  File "xx.py", line 4
    print "yyy\n"
                ^
IndentationError: unindent does not match any outer indentation level

Thus showing that in Python 2.5, tabs are not equal to spaces [and in particular not equal to 4 spaces].

Oops - embarrassing; my proof by counter-example shows that tabs are not equivalent to 4 spaces. As Alex Martelli points out in a comment, in Python 2, tabs are equivalent to 8 spaces, and adapting the example with a tab and 8 spaces shows that this is indeed the case.

x = 1
if x != 1:
^Iprint "x is not 1\n"
        print "y is unset\n"

In Python 2, this code works, printing nothing.

In Python 3, the rules are slightly different [as noted by Antti Haapala]. Compare:

• Python 2 on Indentation
• Python 3 on Indentation

Python 2 says:

First, tabs are replaced [from left to right] by one to eight spaces such that the total number of characters up to and including the replacement is a multiple of eight [this is intended to be the same rule as used by Unix]. The total number of spaces preceding the first non-blank character then determines the line’s indentation. Indentation cannot be split over multiple physical lines using backslashes; the whitespace up to the first backslash determines the indentation.

Python 3 says:

Tabs are replaced [from left to right] by one to eight spaces such that the total number of characters up to and including the replacement is a multiple of eight [this is intended to be the same rule as used by Unix]. The total number of spaces preceding the first non-blank character then determines the line’s indentation. Indentation cannot be split over multiple physical lines using backslashes; the whitespace up to the first backslash determines the indentation.

[Apart from the opening word "First," these are identical.]

Python 3 adds an extra paragraph:

Indentation is rejected as inconsistent if a source file mixes tabs and spaces in a way that makes the meaning dependent on the worth of a tab in spaces; a TabError is raised in that case.

This means that the TAB vs 8-space example that worked in Python 2 would generate a TabError in Python 3. It is best — necessary in Python 3 — to ensure that the sequence of characters making up the indentation on each line in a block is identical. PEP8 says 'use 4 spaces per indentation level'. [Google's coding standards say 'use 2 spaces'.]

Hey Guys,

I've been following a Guide to python where they told us to use Tabs but then they sent us to the PEP8 Style Guide where it states:

"Spaces are the preferred indentation method."

Now, after I digging around a bit I found that you should use 4 spaces to indent code, sooo...

Why not just use Tab instead of hitting the space bar 4 times?

I'm guessing this is a hot topic, but I just wanted to make sure it's ok with going with Tabs over spaces [since it's the same lenght!]. [I'm also a fan of Silicon Valley and as Richard Hendriks says: "2 Tabs save you 8 spaces"!]

def flatten[matrix]:
  return [
            n for row
 in matrix for n
       in row
     ]
              

def len_or_none[obj]:
   try:
         return len[obj]
   except TypeError:
     return None

def guess_number[]:
  while True:
     guess = input['Guess: ']
    if guess == '4':
        break
              

def len_or_none[obj]:
  try:
      return len[obj]
    except TyperError:
      return None

def guess_number[]:
    while True:
	guess = input['Guess: ']
	if guess == '4':
	    break
              

def guess_number[]:
    while True:
        guess = input['Guess: ']
	if guess == '4':
	    break
              

def guess_number[]:
    while True:
	guess = input['Guess: ']
	if guess == '4':
	    break
              

def guess_number[]:
    while True:
	guess = input['Guess: ']
    	if guess == '4':
	    break
              

def progressively_more_spaces[]:
 	print["let's add one more space to the beginning..."]
  	print["of each line."]
   	print["The effective indentation is the same"]
    	print["even though we're adding more spaces."]
     	print["Each tab represents only the spaces needed"]
      	print["to get to the next 8 character tab stop."]
       	if "your editor doesn't use 8 character tabs":
        	print["you may have trouble reading this code."]
         	print["Python uses 8 character tab stops"]
          	print["so we also use 8 character tab stops."]
           	print["This way we can mix spaces and tabs"]
            	print["without any worries about broken code."]
             	print["Mixing tabs and spaces can be fun"]
              	print["but beware!"]
               	while "you could write code like this":
                	print["It's probably best not to."]
              

# //editorconfig.org
[*.py]
indent_size = 4
tab_width = 8
indent_style = tab
          

$ python3 examples/demo.py
  File "examples/demo.py", line 3
    print["of each line."]
                         ^
TabError: inconsistent use of tabs and spaces in indentation
          

How many spaces is a tab in Python?

What are spaces and tabs?

What are tabs Python?

Can you use tab to indent in Python?