Python Learning Note Five: string common operations, dictionaries, three-level menu instances

String Common operations

7 Month Day, 7 Month Day , 7 Month Day, 7 Month Day, 8 Month Day, 2 Month Day

Initial capital: A_str.capitalize ()

Number of statistics strings: A_str.count ("x")

Output character, not enough to fill with the specified character, the center of the character: A_str.center (50, "-")

Determine what the string ends with: A_str.endwith ("XX")

Converts the tab in a string to a specified number of spaces: A_str.expandtabs (tabsize=30)

Finds the position of the specified string in the string: A_str.find ("XX")

The string can also be sliced: A_str[a_str.find ("XX"):]

Formatted output: A_str.format (xx= "x", xxx= "xxx")

Dictionary format output: a_str.format_map ({' name ': ' Alex ', ' Year ': 12})

Determine if it is an Arabic numeral (all English characters +0-9): A_str.isalnum ()

Determine if it is an English character: A_str.isalpha ()

Determine whether it is a decimal number: A_str.isdecimal ()???

Determine whether it is an integer: A_str.isdigit ()

Determine if the identifier is valid (valid variable name): A_str.isidentifier ()

To determine if it is lowercase: a_str.islower ()

Determine if there are only numbers (no decimal points): A_str.isnumeric (), test: "0132". IsNumeric ()

Determine if it is a space: A_str.ispace ()

Determine if the first letter of each word is capitalized: A_str.istitle ()

Determine if it can be printed: a_str.isprintable () #tty file, drive file

To determine if uppercase: A_str.isupper ()

Combines a string list into a string, separated by the specified character: "Specified character". Join (A_str_list)

Outputs a string of the specified length, the string on the left, and insufficient when the specified character (string? ) padding: a_str.ljust (50, ' * ')

Outputs a string of the specified length, the string on the right, and the specified character when insufficient (string? ) padding: a_str.rjust (50, ' * ')

Character lowercase: a_str.lower ()

Character capitalization: A_str.upper ()

Remove the left space carriage return: "Test". Lstrip ()

Remove the right space carriage return: "Test". Rstrip ()

Remove the space on both sides to enter: ' test\n '. Strip () \ r will be?

Converts the specified letter to the corresponding number:

P=str.maketrans ("abcdef", "123456")

Print ("Alex Li". Translate (p))

Replacement string: A_str.replace (' l ', ' l ', 1)

Find character position in string from right to left: A_str.rfind (' x ')

Separates a string into a list by a specified character, without specifying a space: A_str.split ()

Separate strings by carriage return as a list: A_str.splitlines () (\r,\n?). ）

Case conversion: A_str.swapcase ()

Fill in 0 of the string with insufficient parts: A_str.zfill (50)

Dictionary

7.18,7.19,7.21,7.28,8.28,2.28

Key-value

JSON format

Unordered, key is unique, the first example has a curly brace at the end

Value, Info[key],info.get (key)

Determine if key exists, key in Info,python2:info.haskey (key)

Multi-level dictionary nesting, modification, primary level positioning, assignment

Key do not use Chinese

Print all Values,keys,setdefault (), first determine if there is??? , does not exist then creates

Info.update (Info2), merge two dictionaries, key consistent when overwriting old values with new values???

Convert to list, info. Items ()

Fromkeys (alist,value) Create a new dictionary, each value in the list is only key???

Output Key,value:

For key in info:

Print (I,info[i])--efficient

For k,v in Info.items ():

Print (K,V)--low efficiency, first converted to list after output

Level Three Menu instance

Flow chart

Building a dictionary

Cycle

Pass:nothing, I don't mean to do anything.

Homework:

Shopping cart optimization, divided into sellers and buyers two documents

Buyer: The product information exists in the file, each run shows the purchased goods and balances

Sellers: Can add items, modify prices

Python Learning Note Five: string common operations, dictionaries, three-level menu instances