Correct string encoding specification in python-Python Tutorial-php.cn

Correct string encoding specification in python

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Release： 2019-06-17 09:15:58

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In Python, strings are immutable objects (immutable), so a certain character of the string cannot be directly modified. One possible way is to convert the string into a list, modify the elements of the list, and then reconnect it into a string.

Correct string encoding specification in python

The sample code is as follows:

s = &#39;abcdefghijk&#39; #原字符串
l = list(s) #将字符串转换为列表，列表的每一个元素为一个字符
l[1] = &#39;z&#39; #修改字符串的第1个字符为z
newS = &#39;&#39;.join(l) #将列表重新连接为字符串
print(newS)#azcdefghijk 
#修改后的字符串

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String formatting and splicing specifications

[Mandatory ] Except for the simplest case of a b, you should use % or format to format the string.

Explanation

Complex formatting is more intuitive using % or format

Yes: x = a + b
     x = &#39;%s, %s!&#39; % (imperative, expletive)
     x = &#39;{}, {}!&#39;.format(imperative, expletive)
     x = &#39;name: %s; score: %d&#39; % (name, n)
     x = &#39;name: {}; score: {}&#39;.format(name, n)
No:  x = &#39;%s%s&#39; % (a, b)  # use + in this case
     x = &#39;{}{}&#39;.format(a, b)  # use + in this case
     x = imperative + &#39;, &#39; + expletive + &#39;!&#39;
     x = &#39;name: &#39; + name + &#39;; score: &#39; + str(n)

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·[Mandatory] Do not use = splicing characters For string lists, join should be used.

Explanation

Strings in python are unmodifiable objects. Each time = will create a new string, which has poor performance.

Yes: items = [&#39;<table>&#39;]
     for last_name, first_name in employee_list:
         items.append(&#39;<tr><td>%s, %s</td></tr>&#39; % (last_name, first_name))
     items.append(&#39;</table>&#39;)
     employee_table = &#39;&#39;.join(items)
No:  employee_table = &#39;<table>&#39;
     for last_name, first_name in employee_list:
         employee_table += &#39;<tr><td>%s, %s</td></tr>&#39; % (last_name, first_name)
     employee_table += &#39;</table>&#39;

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