Python interview one hundred questions - string and regular expression

table of Contents

1. The string formatting template string
2. Fstring manner using the format string
3. The basic operation of the string
4. The method of delivery to the format string parameters in several ways
5. Let string centered
6. Element value in the connection list
7. Regular expression comprises a date string is determined whether
8. Looking for phone number string
9. Extraction area code telephone number, telephone number and extension number with regular expressions, respectively
10. With regular expression search string All Email
11. Regular expression for all floating point format string
12. Extract the HTML page URL

01. The string formatting template string

Format string by:

1. %format
2. Template string
3. format method
4. fstring

# 模板字符串
# 通过Template对象封装，用 $ 放置一些占位符，并通过substitute方法用实际的值替换这些占位符
from string import Template

template1 = Template('$s真棒，$s真厉害')  # '$s真棒，$s真厉害' 就是模板字符串
print(template1.substitute(s = '我'))	# 我真棒，我真厉害
print(template1.substitute(s = '你'))	# 你真棒，你真厉害

template2 = Template('${h}ello world')	# 用{}将占位符名称括起来，以便和其他单词区分
print(template2.substitute(h = 'abc'))

template3 = Template('$dollar$$相当于$pound￡')	# 若要输出$符号，则用$$
data = {}
data['dollar'] = 20
data['pound'] = 15.3
print(template3.substitute(data))	# 数据可放到字典中，更方便

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02. Use fstring mode format string

# fstring
name = 'Bill'
age = 20
def toAge():
    return age + 1

s = f'我是{name}，今年{age}岁，明年我{toAge()}岁'    #前面加上 f 表明有变量或函数
print(s)
我是Bill，今年20岁，明年我21岁

class Person:
    def __init__(self):
        self.name = 'Mike'
        self.age = 40
    def getAge(self):
        return self.age + 1

person = Person()
s1 = f'我是{person.name}，今年{person.age}岁，明年我{person.getAge()}岁'   #对象内的成员也可以
print(s1)
我是Mike，今年40岁，明年我41岁

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03. The basic operation of the string

# 1：通过索引获取字符串中的某个字符（串）
s1 = 'hello world'
print(s1[1])

# 分片
print(s1[6:9])
print(s1[::2])

# 乘法，重复输出
print(s1 * 2)

# 字符是否在字符串中
print('b' in s1)
print('b' not in s1)

# 获取字符串长度、最大最小值
print(len(s1))
print(max(s1))
print(min(s1))

# 列表同样有用
# 但字符串不可以通过索引修改

04. The method of passing parameters to the format string There are several ways

# 默认方式（传入的参数与{}一一对应）、命名参数和位置参数

# 第二题
s1 = 'Today is {},the temperature is {} degree.'
print(s1.format('Sat', 20))
Today is Sat,the temperature is 20 degree.

s2 = 'Today is {day},the temperature is {degree} degree.'
print(s2.format(degree= 20, day= 'Sun'))
Today is Sun,the temperature is 20 degree.

s3 = 'Today is {day},{},the {} temperature is {degree} degree.'
print(s3.format('abcd', 1234, degree= 24, day= 'Sun'))
Today is Sun,abcd,the 1234 temperature is 24 degree.

s4 = 'Today is {day},{1},the {0} temperature is {degree} degree.'
print(s4.format('abcd', 1234, degree= 24, day= 'Sun'))
Today is Sun,1234,the abcd temperature is 24 degree.

class Person:
    def __init__(self):
        self.age = 20
        self.name = 'Bill'
person = Person()

s5 = 'My name is {p.name},my age is {p.age}.'
print(s5.format(p = person))
My name is Bill,my age is 20.

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05. Let the string centered

# 1：center方法、format方法

# 2：
print('<' + 'hello'.center(30) + '>')
print('<' + 'hello'.center(30, '#') + '>')
<############hello#############>

print('<{:^30}>'.format('hello'))
print('<{:#^30}>'.format('hello'))
<############hello#############>

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06. connecting element values ​​in the list

a = ['a', 'b', 'c', 'd', 'd']
s = '+'
print(s.join(a))	#用s分割a
a+b+c+d+d

# 作用：连接路径
dirs = 'D:', 'A', 'code', 'python', 'test'
print(dirs)	# 元组 ('D:', 'A', 'code', 'python', 'test')
path = '\\'.join(dirs)
print(path)	# D:\A\code\python\test

# 注意：连接的元素必须是字符串类型
n = [1, 2, 3, 4]
s = '+'
print(s.join(n))
Traceback (most recent call last):
  File "D:/A/test.py", line 3, in <module>
    print(s.join(n))
TypeError: sequence item 0: expected str instance, int found

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07. regular expression string contains the date determined

import re # 专门处理正则表达式

print(re.match('hello', 'hello'))
<_sre.SRE_Match object; span=(0, 5), match='hello'>

print(re.match('hello', 'ahello'))
None # 不匹配返回None

print(re.match('.hello', 'ahello'))	# . 表示任意字符
<_sre.SRE_Match object; span=(0, 6), match='ahello'>

print(re.match('.*hello', 'aahello'))	# * 表示任意数量
<_sre.SRE_Match object; span=(0, 7), match='aahello'>

# 第二题
s = 'Today is 2020-02-06.'
m = re.match('.*\d{4}-\d{2}-\d{2}.*', s)	# \d表示数字 {4}表示四位

if m is not None:
    print(m.group())
Today is 2020-02-06.

08. Looking for the phone number string

Difference: match to match, search for search

import re

print(re.match('.*python', 'i love python'))
<_sre.SRE_Match object; span=(0, 13), match='i love python'>
print(re.search('python', 'i love python'))
<_sre.SRE_Match object; span=(7, 13), match='python'>

# 搜索手机号
n = re.search('1\d{10}', 'phone number:12345487899')	# 限制第一位为 1 
if n is not None:
    print(n.group())
    print(n.start())
    print(n.end())
12345487899
13
24

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09. To retrieve a phone number area code, telephone number and extension number with regular expressions, respectively

# 正则表达式分组
import re

n = re.search('(\d{3})-(\d{7,})-(\d{3,})', 'phone number:024-123456789-5446')
#至少7位用 {7,}，分组用（）括起来并且用 n.groups
if n is not None:
    print(n.group())	# 024-123456789-5446
    print(n.groups())	# ('024', '123456789', '5446')
    print(n.groups()[0])	# 024	
    print(n.groups()[1])	# 123456789
    print(n.groups()[2])	# 5446

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10. Using a regular expression search string in all of Email

import re

n = '我的email地址是[email protected]，你的地址是多少？是[email protected]吗？还是[email protected]?'
prefix = '[0-9a-z]+@[0-9a-zA-Z]+\.'
result = re.findall(prefix + 'com|' + prefix + 'net', n, re.I) # I 忽略大小写
# 'com|' 或后面要加完整的正则表达式 不能直接加'net'，要不然就把'net'当条件
print(result)
['[email protected]', '[email protected]']

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11. The regular expression for all floating point format string

import re
'''
1.如何用正则表达式表示浮点数 考虑负数: -?\d+(\.\d+)? （-?表示可能有或没有负数，(\.\d+)?表示可能有或没有小数）
2.格式化浮点数 format
3.如何替换原来的浮点数 sub：只返回替换的结果 subn：返回元组（替换的结果， 替换的次数）
'''
result = re.subn('-?\d+(\.\d+)?', '##', 'Pi is 3.14159265, e is 2.71828183, -0.1 + 1.3 = 1.1')
print(result)	# ('Pi is ##, e is ##, ## + ## = ##', 5)
print(result[0])	# Pi is ##, e is ##, ## + ## = ##
print(result[1])	# 5

def fun(match):
    return '<' + match.group() + '>'

result = re.subn('-?\d+(\.\d+)?', fun, 'Pi is 3.14159265, e is 2.71828183, -0.1 + 1.3 = 1.1')
print(result)	#('Pi is <3.14159265>, e is <2.71828183>, <-0.1> + <1.3> = <1.1>', 5)

def fun(match):
    return format(float(match.group()), '0.2f')

result = re.subn('-?\d+(\.\d+)?', fun, 'Pi is 3.14159265, e is 2.71828183, -0.1 + 1.3 = 1.1')
print(result)
# ('Pi is 3.14, e is 2.72, -0.10 + 1.30 = 1.10', 5)

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12. extract the HTML page URL

import re

s = '<a href="www.baidu.com">百度</a> <a href="www.google.com">谷歌</a>'
result = re.findall('<a[^<]*href="([^<]*)">', s, re.I) #a和href中可能有除了<外的其他东西 [^<}
print(result)
['www.baidu.com', 'www.google.com']
for url in result:
    print(url)
www.baidu.com
www.google.com

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