【dictionary】
# 1 dictionary definition: the key and value were written in the form of data types
# Pros: looks very intuitive, fast value
# Features: Dictionaries are unordered, unlike list
info = {
"guoyanna":"a",
"jingna":"b",
"zhangying":"c",
}
2 dictionary CRUD
A method of increasing 1
info [ "name"] = " sichen" If the key does not exist increases, if the key is present, then changed to modify the value of the
A method of increasing 2
info.setdefault ( "car", "baoma ") If the key exists without modification, directly increase
print(info)
delete
info.pop("guoyanna")
print(info)
del info["jingna"]
print(info)
To delete a random element
info.popitem ()
print(info)
The value
print (info [ "name"] ) # if an error would take absent
print (info.get ( "bucunzai") ) # If the value does not exist to take returns None , the recommended value mode; may be taken when a value less than a given value, written as follows
print(info.get("buzhidao","nan"))
Gets a dictionary of all the key
print(info.keys())
Gets a dictionary of all value
# Dictionary Empty
info.clear()
# Add the dictionary: second dictionary of key and value added to the first dictionary info inside
info.update (second dictionary's name)
# Determine whether the dictionary has a key: returns true or false
Print ( "Key name " in info)
# Judge a key if there is
print("zhangying"in info)
Direct circulation dictionary, then, is to take the dictionary key
for i in dictionary name :
print(i)
While taking a dictionary key and value values:
for key, value in the dictionary name .items ():
print("%s => %s”%(key,value))
Circular list - all elements inside output
l = [ 'liuzhao', 'liudonghai', 'zhaowenming', 'xiaoming', 'users']
for i in l:
print(i)
String cycle - an output element which
a = "hello"
for i in a :
print(i)
Commonly used method [string]
1 to remove the string inside the left and right sides of spaces:
Print (String. Strip )
2 to remove the spaces around the string
Left blank: string L. Strip
The right space . Strings. Rstrip
3 replacement string values inside
print (s.replace ( " old values ", " the value you want to change "))
4 to remove the intermediate space string
print(s.replace(" ",""))
5 to find the number of times a character appears
print(s.count("c"))
6 for a string inside the element index
print (s.index ( "a") ) # find a non-existent element will complain
print (s.find ( "a") ) # can not find returns -1 , not being given
7 boolean value: false to true
8 verify the correctness of returns true / false
print ( variable .startswith ( "a")) # authentication string is not in a start
print ( variable .endswith ( ". jpg")) # verification is not in the picture in .jpg format at the end
9 content output string to upper case
Variable .upper ()
10 lowercase string contents are output:
Variable .lower ()
11 yuan group
11-001: Content tuples which are not to be modified
11-002: If there is only one element tuple, then after the element must be added a comma
11-003: represents tuple: t = (1,2,3)
11-004: About two methods tuples: View the number of elements appear: t.count ( "element name"); t.index (subscript view elements)
Element 12 inside the string comma-separated by the following method, the string can be divided, a list of output - to what string element split, the split symbols which method is what, if not prevail string format
Variable .split ( ",")
13 string into a list of elements inside, to facilitate post writable Dictionary - segmented elements output symbol string is determined by the preceding join that symbol
L = [ "guo", "ya", "nan"]
Print (“,”join(L))
Read mode: r
You can only read, can not write, open a nonexistent file will complain
Write mode: w
Only write, it will overwrite the contents of a file before; if the file does not exist create your own
Append mode: a
In the original contents of the file based on the new content can be increased written, written in the last; if they will create the file does not exist
Read-write mode: r +
Read-write mode: w +
Additional read mode: a +
- efficient processing of files
1 using the cycle of operation for a file, each line may be obtained directly outputs the content file
- Modify the contents of the file
The first method: first read the contents, then replaced, remove the original contents of the file, the new content to write into
The second method: progressive process;
A first open a file, read a line written to modify a file inside an empty b from a file, delete a file, change the name of the file b is a file name
The benefits of using an open file with conduct
No need to manually close the file, it will automatically shut off when the need