python基础

1.1 字符串函数

字符串可以包含在单引号、双引号、3个单引号、3个双引号之间。

split() --将一个字符串拆分成一个子字符串列表。

string1 = "My deliverable is due in may"
string1_list1 = string1.split()
string1_list2 = string1.split(" ",2)
print("Output #11 :{0}".format(string1_list1))
print("Output #12 :{0}".format(string1_list2))
string2 = "Your,deliverable,is,due,in,june"
string2_list = string2.split(',')
print("Output #13 :{0},{1},{2}".format(string2_list[1],string2_list[5],string2_list[-1]))

--------------结果

Output #11 :['My', 'deliverable', 'is', 'due', 'in', 'may']
Output #12 :['My', 'deliverable', 'is due in may']
Output #13 :deliverable,june,june

join() ---将列表中的子字符串合成一个字符串

print("Output #14 :{0}".format(','.join(string2_list)))

Output #14 :Your,deliverable,is,due,in,june

strip() --两侧删除空格、制表符和换行符，lstrip() --左侧删除空格、制表符和换行符，rstrip() --右侧删除空格、制表符和换行符

string3 = " Remove unwanted character from this string. "
print("Output #1: string3: {0:s}".format(string3))
string3_lstrip = string3.lstrip()
print("Output #2: lstrip: {0:s}".format(string3_lstrip))
print("Output #3: rstrip: {0:s}".format(string3.rstrip()))
print("Output #4: strip: {0:s}".format(string3.strip())

Output #1: string3:  Remove unwanted character  from this string.		   

Output #2: lstrip: Remove unwanted character  from this string.		   

Output #3: rstrip:  Remove unwanted character  from this string.
Output #4: strip: Remove unwanted character  from this string.

replace() --将字符串中的一个或一组字符替换为另一个或另一组字符。

lower(),upper(),capitalize()--lower,upper分别用来将字符串中的字母转换为小写和大写。capitalize将字符串中的第一个字母应用upper函数，其余字母应用lower函数。

1.2正则表达式与模式匹配

import re
string="The quick brown fox jumps over the lazy dog."
string_list = string.split()
pattern = re.compile(r"The",re.I)
count = 0
for word in string_list:
if pattern.search(word):
count += 1
string_list = string.replace("The","THE")
print("Output #1 :{0:d}".format(count))
print(string_list)

   Output #1 :2

THE quick brown fox jumps over the lazy dog.

re.compile()将文本形式的模式编译成为编译后的正则表达式。re.I函数确保模式是不区分大小写的，原始字符串r可以确保python不处理字符串的转义字符。

#在字符串中每次找到模式时将其打印出来 

import re
string="The quick brown fox jumps over the lazy dog."
string_list = string.split()
pattern = re.compile(r"(?P<match_word>The)",re.I)
print("Output #2:")
for word in string_list:
if pattern.search(word):
print("{:s}".format(pattern.search(word).group('match_word')))

  

Output #2:
The
the

#使用字母"a"替换字符串中的单词"the"

import re
string="The quick brown fox jumps over the lazy dog."
string_to_find = r"The"
pattern = re.compile(string_to_find,re.I)
print("Output 2#: {:s}".format(pattern.sub("a",string)))

Output 2#: a quick brown fox jumps over a lazy dog.

1.3日期

#!/usr/bin/env python3
from math import exp,log,sqrt
import re
from datetime import date,time,datetime,timedelta
today = date.today()
print("{0!s}".format(today))
print("{0!s}".format(today.year))
print("{0!s}".format(today.month))
print("{0!s}".format(today.day))
current_datetime = datetime.today()
print("{0!s}".format(current_datetime))
one_day = timedelta(days=-1)
yesterday = today + one_day
print("{0!s}".format(one_day))
print("{0!s}".format(yesterday))
eight_hours = timedelta(hours=-8)
print("{0!s} {1!s}".format(eight_hours.days,eight_hours.seconds))
date_diff = today - yesterday
print("{0!s}".format(date_diff))
print("{0!s}".format(str(date_diff).split()[0]))
#根据一个日期对象创建具有特定的字符串
print("{:s}".format(today.strftime('%m/%d/%Y')))
date1 = today.strftime('%m/%d/%Y')
print("{!s}".format(datetime.strptime(date1,'%m/%d/%Y')))

2020-06-17
2020
6
17
2020-06-17 22:12:06.147000
-1 day, 0:00:00
2020-06-16
-1 57600
1 day, 0:00:00
1
06/17/2020
2020-06-17 00:00:00