问题标题 - 在Python中包装一个字符串

Question

我有一个字符串的名字,在这个例子中是"markus johansson".

我正在尝试编写一个使'm'和'j'大写的程序:

name = "markus johansson"

for i in range(1, len(name)):
    if name[0] == 'm':
        name[0] = "M"
    if name[i] == " ":
        count = name[i] + 1
    if count == 'j':    
            name[count] = 'J'  

我很确定这应该可行,但它给了我这个错误:

File "main.py", line 5 in <module> 
   name[0] = "M" 
TypeError: 'str' object does support item assignment 

我知道有一个名为.title()的库函数,但我想做"真正的编程".

我该如何解决？

Answer 1

我想你想要达到的目标是:

from string import capwords
capwords(name)

产量:

'Markus Johansson'

编辑:好的,我看到你要打开一扇门.这是低级别的实现.

''.join([char.upper() if prev==' ' else char for char,prev in zip(name,' '+name)])

Answer 2

>>> "markus johansson".title()
'Markus Johansson'

内置字符串方法是可行的方法.

编辑:我看到你想重新发明轮子.任何特殊原因？您可以选择任意数量的复杂方法,例如:

' '.join(j[0].upper()+j[1:] for j in "markus johansson".split())

标准库仍然是可行的方法.

Answer 3

string.capwords()(定义于string.py)

# Capitalize the words in a string, e.g. " aBc  dEf " -> "Abc Def".
def capwords(s, sep=None):
    """capwords(s, [sep]) -> string

    Split the argument into words using split, capitalize each
    word using capitalize, and join the capitalized words using
    join. Note that this replaces runs of whitespace characters by
    a single space.

    """
    return (sep or ' ').join(x.capitalize() for x in s.split(sep))

str.title()(定义于stringobject.c)

PyDoc_STRVAR(title__doc__,
"S.title() -> string\n\
\n\
Return a titlecased version of S, i.e. words start with uppercase\n\
characters, all remaining cased characters have lowercase.");
static PyObject*
string_title(PyStringObject *self)
{
    char *s = PyString_AS_STRING(self), *s_new;
    Py_ssize_t i, n = PyString_GET_SIZE(self);
    int previous_is_cased = 0;
    PyObject *newobj = PyString_FromStringAndSize(NULL, n);
    if (newobj == NULL)
        return NULL;
    s_new = PyString_AsString(newobj);
    for (i = 0; i < n; i++) {
        int c = Py_CHARMASK(*s++);
        if (islower(c)) {
            if (!previous_is_cased)
                c = toupper(c);
            previous_is_cased = 1;
        } else if (isupper(c)) {
            if (previous_is_cased)
                c = tolower(c);
            previous_is_cased = 1;
        } else
            previous_is_cased = 0;
        *s_new++ = c;
    }
    return newobj;
}

str.title() 在纯Python中

class String(str):
    def title(self):
        s = []
        previous_is_cased = False
        for c in self:
            if c.islower():
               if not previous_is_cased:
                  c = c.upper()
               previous_is_cased = True
            elif c.isupper():
               if previous_is_cased:
                  c = c.lower()
               previous_is_cased = True
            else:
               previous_is_cased = False
            s.append(c)
        return ''.join(s)

例:

>>> s = ' aBc  dEf '
>>> import string
>>> string.capwords(s)
'Abc Def'
>>> s.title()
' Abc  Def '
>>> s
' aBc  dEf '
>>> String(s).title()
' Abc  Def '
>>> String(s).title() == s.title()
True