为列表中的每个字符串附加字符串长度

Question

Input

strlist = ['test', 'string']

Desired output:

strlist = [('test', 4), ('string', 6)] 

Attempt 1:

def add_len(strlist):
    for i, c in enumerate(strlist):
        strlist += str(len(strlist))
    return strlist

Attempt 2:

def add_len(strlist):
    for c in strlist:
        c += " " + str(len(c))
    return strlist

I realise I have the following issues:

• Attempt 1: This results in an infinite loop, as the code keeps adding onto the list.

• Attempt 2: This does not add the value to the string, however, when I do, I get the infinite loop issue from #1.

I believe I need to evaluate the number of elements in the list first and implement a while statement, but not quite sure how to do this.

Answer 1

Use a list comprehension:

strlist = ['test', 'string']

def add_len(strlist):
    return [(s, len(s)) for s in strlist]

Answer 2

You can use a list comprehension like this.

def add_len(strlist):
    return [(s, len(s)) for s in strlist]

Or expanded,

def add_len(strlist):
    new_list = []
    for s in strlist:
        new_list.append((s, len(s)))
    return new_list

In the expanded form we can see the steps it's going through a bit more clearly.

1. Create list new_list to put your strings and lengths into.
2. Iterate over each string in strlist .
3. For each string, append the string and its length to new_list .
4. Return new_list .

Of course, both of these gives you your desired output:

[('test', 4), ('string', 6)]

Answer 3

Using map() :

>>> strlist
['test', 'string']

>>> list(map(lambda x: (x, len(x)), strlist))
[('test', 4), ('string', 6)]

Answer 4

for i, c in enumerate(strlist)

The i is the index of the element in the string list, and the c the value of the element. And you keep on appending the results in place ( strlist ), so that the strlist keeps growing.

While the second attempt won't output your desired results. The result will be strlist = ['test 4', 'string 6'] . Every single element is not made up of tuple .

Meanwhile both the two attempts modify strlist in place, which will bring in potential issues (affect other attributes/parameters that refer to strlist ).

A better solution for this is using list comprehension.

strlist = ['test', 'string']
new_strlist = [(s, len(s)) for s in strlist]