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Module string.py in Python

不言Original: 2018-06-01 16:41:491068browse

This article mainly introduces the relevant information of the string.py module in Python. The introduction in the article is very detailed and has certain reference value for everyone. Friends who need it can take a look below.

1. Usage

String constant:

import string

print(string.ascii_lowercase)
print(string.ascii_uppercase)
print(string.ascii_letters)
print(string.digits)
print(string.hexdigits)
print(string.octdigits)
print(string.punctuation)
print(string.printable)

Result

abcdefghijklmnopqrstuvwxyz
ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
0123456789
0123456789abcdefABCDEF
01234567
!"#$%&&#39;()*+,-./:;<=>?@[\]^_`{|}~
0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&&#39;()*+,-
 ./:;<=>?@[\]^_`{|}~

## 2. Template class:

In fact, the Template class can be compared with the usage of formatted strings and the

format() method of string objects, which can help better understanding. First, create a new python file: string_template.py,

and then write the following content in it:

import string

values = {&#39;var&#39;: &#39;foo&#39;}

t = string.Template("""
Variable : $var
Escape  : $$
Variable in text: ${var}iable
""")

print(&#39;TEMPLATE:&#39;, t.substitute(values))

s = """
Variable : %(var)s
Escape  : %%
Variable in text: %(var)siable
"""

print(&#39;INTERPOLATION:&#39;, s % values)

s = """
Variable : {var}
Escape  : {{}}
Variable in text: {var}iable
"""

print(&#39;FORMAT:&#39;, s.format(**values))

Then, enter in the python command line:

$ python string_template.py

Result

TEMPLATE:
Variable : foo
Escape  : $
Variable in text: fooiable

INTERPOLATION:
Variable : foo
Escape  : %
Variable in text: fooiable

FORMAT:
Variable : foo
Escape  : {}

You can see that all three can have the effect of formatting strings. It's just that the modifiers of the three are different. The good thing about the Template class is that it can inherit the class and customize its modifiers after instantiation, and it can also define regular expressions for the name format of variables.

Such as string_template_advanced.py example:

import string
class MyTemplate(string.Template):
 delimiter = &#39;%&#39;
 idpattern = &#39;[a-z]+_[a-z]+&#39;


template_text = &#39;&#39;&#39;
 Delimiter : %%
 Replaced : %with_underscore
 Igonred : %notunderscored
&#39;&#39;&#39;


d = {
 &#39;with_underscore&#39;: &#39;replaced&#39;,
 &#39;notunderscored&#39;: &#39;not replaced&#39;,
}

t = MyTemplate(template_text)
print(&#39;Modified ID pattern:&#39;)
print(t.safe_substitute(d))

First, explain the above python file. A class MyTemplate is defined inside, which inherits the Template class of string, and then overloads its two fields: Delimiter is the modifier, now specified as '%' instead of the previous '$'. Next, idpattern is the format specification for the variable.

Result

$ python string_template_advanced.py
Modified ID pattern:

 Delimiter : %
 Replaced : replaced
 Igonred : %notunderscored

Why is notunderscored not replaced? The reason is that when we define the class, we specify that the underscore '_' should appear in the idpattern, but the variable name does not have an underscore, so it cannot be replaced.

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