3.1.4 template string, 3.1.4 string

3.1.4 template string, 3.1.4 string

Replace strings in strings. % s is generally used for formatting. However, this formatting method is complicated and error-prone even for familiar developers. To solve these problems, a template class is provided in the string library. For more information, see PEP 292. The template class string mainly uses the replacement string starting with $ to replace the string starting with %.

The rules for replacing strings are as follows:

L $, two $ represents a $ character output.

L $ identifier: identifies and replaces the string position and key value with $. Identifier is the key of the key-value pair in the function.

L $ {identifier}. When the string to be replaced is followed by a string, braces must be used to separate the strings to identify the key of the key-value pair. For example, $ {identifier} abc, because abc is followed by the string to be replaced.

When a string starting with $ cannot be replaced during the replacement process, a ValueError exception is thrown.

Class string. Template (template)

The constructor is used to construct a replaceable template string.

 

Substitute (mapping, ** kwds)

This function is used to replace the placeholder string in the template string and return a new string. The mapping parameter can be used to input dictionary objects. The kwds parameter can be used to input key-value pairs. The name of the string to be replaced in the string is the same as that in the dictionary or as that in the key-value pair.

 

Safe_substitute (mapping, ** kwds)

The parameters and functions of this function are the same as those of the above substitute function. The only difference is that when you find a replacement string, the corresponding replacement string is not found, in the substitute function, ValueError and KeyError are thrown and cannot be replaced. In the safe_substitute function, an exception is thrown, but the output can be continued. The replaced string is not changed.

 

Example:

# Template

 

From string import Template

 

S = Template ('$ who like apple ')

Print (s. substitute (who = 'Tom '))

 

S = Template ('$ {who} abc: $ who like apple ')

Print (s. substitute (who = 'Tom '))

Print (s. safe_substitute ())

The output is as follows:

$ Tom like apple

$ Tomabc: Tom like apple

$ {Who} abc: $ who like apple

 

3.1.5 string auxiliary functions

String. capwords (s, sep = None)

This function uses str. split () function to split the parameter s string, and then use str. the capitalize () function is used to format the substring into the first letter and the other letters in the lower-case format. Finally, str is used. join () concatenates formatted substrings. If the sep parameter is set to None or is not given during the connection, a space is used by default to separate the substrings and output characters; otherwise, the given letter is used as the separator for recognition and output.

 

Example:

 

Import string

S = 'abc face CHINA shenzhen'

Print (string. capwords (s ))

 

S = 'the quick brown fox jumped over The lazy dog .'

Print (string. capwords (s ))

 

Print (string. capwords ('abc # abc # test # dog', sep = '#'))

The output result is as follows:

Abc Face China Shenzhen

The Quick Brown Fox Jumped Over The Lazy Dog.

Abc # Test # Dog

 

 

Cai junsheng QQ: 9073204 Shenzhen

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