python string

raw strings

在字符串前面加r，将忽略所有的逃逸字符

print(r'That is Carol\'s cat.')
# 输出为
That is Carol\'s cat.

mulitline strings with triple quotes

用三个单引号或者三个双引号，可以引用多行字符串

print('''Dear Alice,

Eve's cat has been arrested for catnapping, cat burglary, and extortion.

Sincerely,
Bob''')

多行注释

"""This is a test Python program.
Written by [email protected]

This program was designed for Python 3, not python 2.
"""

def spam():
    """This s a multipline comment to help
       explain what the spam() function doese."""
    print('Hello!')


spam()

indexing and slicing strings

spam = 'Hello world!'
print(spam[0])
print(spam[4])
print(spam[4:])
print(spam[-1])
print(spam[:5])
print(spam)

The　isX String methods

• isalpha() 如果string只包含字母，并且没有空格
• isalnum() 如果string只包含字母和数字，并且没有空格
• isdecimal() 如果string只包含数字，并且没有空格
• isspace() 如果string 只包含spaces, tabs 和 newlines. and is not blank
• istitle() 如果string包含的单词的第一个字母都是大写。

startswith() 和 endswith()

判断字符串是否以给定的字符串作为还是或结束。

The join() and split() String Methods

join　以给定的字符或者字符串，讲数值里面的字符串链接起来

spam = ['cats', 'rats', 'bats']
print(', '.join(spam))

spam = ['My', 'name', 'is', 'Huxing']
print(' '.join(spam))

print('ABC'.join(spam))

split 以给定的字符或者字符串将目标字符串拆分成一个数组。如果不指定字符串，默认会易空格作为拆分标识。

spam = 'These white space characters are not included in the strings in the returned list.'
print(spam.split())

# 输出内容为
['These', 'white', 'space', 'characters', 'are', 'not', 'included', 'in', 'the', 'strings', 'in', 'the', 'returned', 'list.']

Justifying Text with rjust(), ljust(), and center()

spam = 'Hello'
print(spam.rjust(10))
print(spam.rjust(20))

spam = 'Hello World'
print(spam.rjust(20))
print(spam.ljust(10))

print(spam.rjust(20,'*'))
print(spam.ljust(20,'-'))

print(spam.center(20))
print(spam.center(20, '='))

# 输出的内容是
     Hello
               Hello
         Hello World
Hello World
*********Hello World
Hello World---------
    Hello World     
====Hello World=====

打印菜单

def printPicnic(itemsDict, leftWidth, rightWidth):
    print('PICNIC ITEMS'.center(leftWidth + rightWidth, '-'))
    for k, v in itemsDict.items():
        print(k.ljust(leftWidth, '.') + str(v).rjust(rightWidth))

picnicItems = {'sandwiches': 4, 'apples': 12, 'cups': 4, 'cookies': 8000}
printPicnic(picnicItems, 12, 5)
printPicnic(picnicItems, 20, 6)


# 输出内容是
---PICNIC ITEMS--
cups........    4
sandwiches..    4
cookies..... 8000
apples......   12
-------PICNIC ITEMS-------
cups................     4
sandwiches..........     4
cookies.............  8000
apples..............    12

removing whitespaces with strip(), rstrip(), and lstrip()

• strip() will return a new string without any whitespace characters at the beginning or end.
• lstrip() remove whitespace characters from the left ends.
• rstrip() remove whitespace characters from the right ends.

spam = '     Hello World     '
print(spam.strip())
print(spam.lstrip())
print(spam.rstrip())

spam = 'SpamSpamBaconSpamEggsSpamSpam'
print(spam.strip('ampS')) #移除字符串中以a m p 或者 S 开始或结束的部分

# 输出内容是
Hello World
Hello World     
     Hello World
BaconSpamEggs

pyperclip 　将字符串弄到粘贴板上

# 先安装pip
sudo apt-get install python3-pip
# 再安装 pyperclip module
sudo pip3 install pyperclip
# 安装依赖
sudo apt install xsel

代码如下

import pyperclip
pyperclip.copy('Hello world!')
pyperclip.paste()

粘贴板文字处理

从网上拷贝一段文字在粘贴板上，然后运行程序，再在另外一个地方粘贴

#! /usr/bin/python3
# bulletPointAdder.py - Adds Wikipedia bullet points to the start
# of each line of text on the clipboard.

import pyperclip
text = pyperclip.paste()

# TODO: Separete lines and add starts.
text_array = text.split('\n')
start_text = []
for line in text_array:
    start_text.append('* ' + line)
past_text = '\n'.join(start_text)      

pyperclip.copy(past_text)



### 书里面给的答案
#! /usr/bin/python3
import pyperclip
text = pyperclip.paste()

# Separete lines and add stars.
lines = text.split('\n')
for i in range(len(lines)):  # loop through all indexes for "lines" list
    lines[i] = '* ' + lines[i] # add star to each string in "lines" list
text = '\n'.join(lines)
pyperclip.copy(text)

Table Printer

#! /usr/bin/python3

tableData = [['apples', 'oranges', 'cherries', 'banana'],
             ['Alice', 'Bob', 'Carol', 'David'],
             ['dogs', 'cats', 'moose', 'goose']]

def printTable(tableData):
    max_width = []
    for i in range(len(tableData)):
       max_width.append(0)
       for j in range(len(tableData[i])):   
          word = tableData[i][j]
          if len(word) > max_width[i]:
               max_width[i] = len(word) 
    for j in range(len(tableData[0])):
        for i in range(len(tableData)):
            word = tableData[i][j]
            print(word.rjust(max_width[i]), end=' ')  
        print('')


printTable(tableData)

输出内容如下

  apples Alice  dogs 
 oranges   Bob  cats 
cherries Carol moose 
  banana David goose