Python 2.7计算字符串数

Question

I'm trying to count the number of times in a list a string has more than 20 characters.

I am trying to use the count method and this is what I keep getting:

>>> for line in lines:
        x = len(line) > 20
        print line.count(x)

edit: sorry for the indentation mistake before

Answer 1

Think you mean this,

>>> s = ['sdgsdgdsgjhsdgjgsdjsdgjsd', 'ads', 'dashkahdkdahkadhaddaad']
>>> cnt = 0
>>> for i in s:
        if len(i) > 20:
            cnt += 1


>>> cnt
2

or

>>> sum(1 if len(i) > 20 else 0 for i in s)
2

or

>>> sum(len(i) > 20 for i in s)
2

Answer 2

In this case,

x = len(line) > 20

x is a boolean, which cannot be "counted" in a string.

>>> 'a'.count(False)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: expected a character buffer object

You need to actually have a string or similar type (Unicode, etc.) to be counted in the line.

Answer 3

I'd recommend using a simple counter for your purpose:

count = 0
for line in lines:
    if len(line) > 20:
        count += 1
print count

Answer 4

>>> for line in lines:
...     x = len(line) > 20

here, x is a boolean type ( True or False in Python), because len(line) > 20 is a logic expression.

You may figure out the problem by debugging:

>>> for line in lines:
...     x = len(line) > 20
...     print x

Besides, x = len(line) > 20 is not a condition expression. You need to use if expression:

>>> count = 0
>>> for line in lines:    
...     if len(line) > 20:
...         count += 1    
... 
>>> print count