Introduction to Python module string.py

This article talks about the Python module string.pyIntroduction

Usage

1. StringConstant:

   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
!"#$%&'()*+,-./:;96b4fef55684b9312718d5de63fb7121?@[\]^_`{|}~
0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&'()*+,-
    ./:;96b4fef55684b9312718d5de63fb7121?@[\]^_`{|}~

1.Template class:

In fact, the Template class can be compared with the usage of formatted string and the format() method of stringobject, which can help better understand. First, create a new python file: string_template.py,
Then write the following content in it:

import string

values = {'var': 'foo'}

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

print('TEMPLATE:', t.substitute(values))

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

print('INTERPOLATION:', s % values)

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

print('FORMAT:', 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 through , define its modifiers automatically after instantiation, and the name format of the variable can also be Definition of regular expression. For example, string_template_advanced.py example:

import string

class MyTemplate(string.Template):
    delimiter = '%'
    idpattern = '[a-z]+_[a-z]+'


template_text = '''
    Delimiter : %%
    Replaced  : %with_underscore
    Igonred   : %notunderscored
'''


d = {
    'with_underscore': 'replaced',
    'notunderscored': 'not replaced',
}

t = MyTemplate(template_text)
print('Modified ID pattern:')
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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