I. Getting to Know Regular Expressions
Regular expression is a special sequence of characters, a string whether we set such a sequence of characters, match the fast retrieval of text, the realization of the operation of replacing text
json (xml) Lightweight web data exchange format
import re
a='C|C++|Java|C#||Python|Javascript'
r= ('Python',a)
print(r)
if len(r) > 0:
print('String with Python in it')
else:
print('No')
['Python']
String containingPython
II. Metacharacters and ordinary characters
import re
a='C0C++7Java8C#9Python6Javascript'
r= ('\d',a)
print(r)
b=''
for x in a:
try:
int(x)
b +=x+','
except :
pass
print(b)
Results:
['0', '7', '8', '9', '6']
0,7,8,9,6,
'Python' normal character '\d' meta character
III. Character sets
import re
# Find words whose middle character isn't a C or an F #
s = 'abc, acc, adc, aec, afc, ahc'
r = ('a[^cf]c', s) #[a-z] [cf]
print(r)
Results:
['abc', 'adc', 'aec', 'ahc']
IV. Generalized character sets
#\d Numbers \D Letters
#\w Numbers and letters = [a-zA-Z0-9_] \W
#\s Blank characters \S
a='python 11\t11java&678p\nh\rp'
r = ('\s', a)
print(r)
Results:
[' ', '\t', '\n', '\r']
V. Quantifiers
a='python 1111java&678php'
r = ('[a-z]{3,6}', a)
print(r)
Results:
['python', 'java', 'php']
VI. Greed and non-greed
a='python 1111java&678php'
r = ('[a-z]{3,6}?', a)
#Greedy vs. non-greedy ?
print(r)
Results:
['pyt', 'hon', 'jav', 'php']
VII. Match 0 times 1 time or an unlimited number of times
# * Match 0 or infinitely many times
# + Match 1 or infinitely many times
# ? Match 0 or 1 times
a='pytho0python1pythonn2pythonw'
r = ('python*', a)
print(r)
Results:
['pytho', 'python', 'pythonn', 'python']
VIII. Boundary Matchers
qq = '12345678'
# 4~8
r = ('^\d{4,8}$', qq)
print(r)
a = '123456789'
# 4~8 ^Rules$ ^beginning $end
e = ('^\d{4,8}$', a)
print(e)
Results:
['12345678']
[]
IX. Groups
# () Group
a = 'pythonpythonpythonpythonpython'
#
r = ('(python){3}', a)
print(r)
Results:
['python'] means that there exists a set of (pythonpythonpythonpython) such data
X. Matching model parameters
# I | S ignore case | match all characters
lanuage = 'PythonC#\nJavaPHP'
r = ('c#.{1}', lanuage, | )
print(r)
Results:
['C#\n']
XI. Regular substitution
Search Replacement
def convert(value):
matched = ()
# print(value) <_sre.SRE_Match object; span=(6, 8), match='C#'>
return '!!'+matched+'!!'
lanuage = 'PythonC#JavaC#PHPC#'
# r = ('C#', 'GO', lanuage, 1) Returns: PythonGOJavaC#PHPC#
# s=('C#', 'GO')
r = ('C#', convert, lanuage) #Pass in parameters
print(r)
Results:
Python!!C#!!Java!!C#!!PHP!!C#!!
XII. Passing functions as parameters
def convert(value):
matched = () # Get the value of the object
# print(value) <_sre.SRE_Match object; span=(6, 8), match='C#'>
if int(matched) >=6 :
return '9'
else:
return '0'
lanuage = 'A8C3721D86'
r = ('\d', convert, lanuage)
print(r)
#
A9C0900D99
XIII, search and match function
s = 'A8C3721D86'
# None Match from the beginning If no match is found, return None Match only once.
r = ('\d', s)
print(r) #None
# Search the string and return once the first match is found Match only once
r1 = ('\d', s)
print(r1) #<_sre.SRE_Match object; span=(1, 2), match='8'>
print(()) #8
print(()) # (1, 2)
r2 = ('\d', s)
print(r2) #['8', '3', '7', '2', '1', '8', '6']
xiv. grouping
# Extract the value between life and python #
s = 'life is short,i use python'
#None
r = ('life.*python', s)
print(()) #life is short,i use python group(batch number)
r = ('life(.*)python', s)
print((0)) #life is short,i use python group(batch number)
print((1)) # is short,i use
#group(0) A special case Match the result of the full regular expression
r = ('life(.*)python', s)
print(r) #[' is short,i use ']
s = 'life is short,i use python, i love python'
r = ('life(.*)python(.*)python', s)
print((0)) # life is short,i use python, i love python
print((1)) # is short,i use
print((2)) # , i love
print((0,1,2)) #('life is short,i use python, i love python', ' is short,i use ', ', i love ')
print(()) # (' is short,i use ', ', i love ')
XV. Some suggestions for learning regularization
#\d Numbers \D Letters #\w Numbers and letters = [a-zA-Z0-9_] \W #\s Blank characters \S # . Matches all characters except the newline character \n # * Match 0 or infinitely many times # + Match 1 or infinitely many times # ? Match 0 or 1 times # () Group # I | S ignore capitals | Match all characters
python : crawler, data processing
Understanding JSON
JSON is a lightweightdata exchange format
Strings are JSON representations
A string that conforms to the JSON format is called a JSON string.
{"name":"qiyue"}
JSON VS XML
Advantage:
Cross-language exchange of data
easy-to-read
easy to analyze
High network transmission efficiency
XVII. Deserialization
import json
# JSON object array
json_str = '{"name":"qiyue","age":18}'
s = (json_str)
# dict
# Deserialization
s = (json_str) #load() converts json datatypes to our own language datatypes.
print(type(s)) #<class 'dict'>
print(s) #{'name': 'qiyue', 'age': 18}
print(s['name']) # qiyue
json_str = '[{"name":"qiyue","age":18},{"name":"qiyue","age":18}]'
s = (json_str)
print(type(s)) # <class 'list'>
print(s) # [{'name': 'qiyue', 'age': 18}, {'name': 'qiyue', 'age': 18}]
JSON Python
object dict
array list
string str
number int
number float
true True
false False
null None
XVIII. Serialization
# Serialize to json
student = [
{"name":"qiyue","age":18, 'flag':False},
{"name":"python","age":18}
]
json_str = (student)
print(type(json_str)) # <class 'str'>
print(json_str) #[{"name": "qiyue", "age": 18, "flag": false}, {"name": "python", "age": 18}]
XIX, a small talk JSON, JSON objects and JSON strings
JSON is a lightweightdata exchange format
JSON objects Limited to languages
JSON String
JSON has its own data types
Although it's somewhat similar to JavaScript's data types, they're not the same language.
ECMASCRIPT a standard JavaScript ActionScription JSON a solution to implement the standard
REST service
summarize
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