期望一个缩进的块python

Question

>>> words = ['cat', 'window', 'defenestrate']
>>> for w in words:
... print w, len(w)
  File "<stdin>", line 2
    print w, len(w)
        ^
IndentationError: expected an indented block
>>> print w, len(w)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'w' is not defined
>>> for w in words:
... print w, len(w)
  File "<stdin>", line 2
    print w, len(w)
        ^
IndentationError: expected an indented block

I'm learning Python though main doc. This chapter (4.2. for Statements) .But when i'm practicing it on UBUNTU TERMINAL it gave me above error ? what's that mean ?

Answer 1

As it says, your print statement needs to be indented since it is in a for loop

>>> words = ['cat', 'window', 'defenestrate']
>>> for w in words:
...     print w, len(w)
cat 3
window 6
defenestrate 12

In python, indentations are not simply for readability, they are a requirement. The following two are NOT the same thing

if 1==1:
print 'yes'   #incorrect indentation, not accepted by python

AND

if 1==1:
    print 'yes'   #correct indentation, accepted by python

Indentation is basically placing whitespaces before certain lines in your code with tab or space