Python Dictionary and Collection operations

Dictionary operations

A key-value data type, used as a dictionary of our school, to check the details of the corresponding page by strokes and letters.

Grammar:

info = {    's1'"Jack",    '  S2'"musker",    's2  '"Lili",}

Features of the dictionary:

• Dict is disordered.
• Key must be unique and so is inherently heavy

Increase

>>> info['S4'] ="Wangwu">>>info{'S2':'Lili','S1':'Jack','S4':'Wangwu'}

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Modify

>>> info['S3'] ="Lili">>>info{'S2':'Lili','S3':'Lili','S1':'Jack','S4':'Wangwu'}

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Delete

>>> Info.pop ('S1')'Jack'>>>info{'S2':'Lili','S3':'Lili','S4':'Wangwu'}>>>delinfo['S3']>>>info{'S2':'Lili','S4':'Wangwu'}>>>Info.popitem () ('S2','Lili')>>>info{'S4':'Wangwu'}

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Find

>>>'S2' inchInfo#Standard usageTrue>>> Info.get ('S2')#Get'Lili'>>> info['S2']#ditto, but look underneath.'Lili'>>> info['S5']#If a key does not exist, it will be an error, get will not, not exist only return noneTraceback (most recent): File"<pyshell#15>", Line 1,inch<module>info['S5']keyerror:'S5'

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Other operations

#Values>>>info.values () dict_values (['Lili','Jack'])#Keys>>>Info.keys () Dict_keys (['S2','S1'])#SetDefault>>> Info.setdefault ('S6','Musker')'Musker'>>>info{'S2':'Lili','S6':'Musker','S1':'Jack'}>>> Info.setdefault ('S2','Wangwu')'Lili'>>>info{'S2':'Lili','S6':'Musker','S1':'Jack'}#Update>>>info{'S2':'Lili','S6':'Musker','S1':'Jack'}>>> B = {1:'a', 2:'b'}>>>Info.update (b)>>>info{'S2':'Lili', 1:'a', 2:'b','S6':'Musker','S1':'Jack'}#Items>>>Info.items () dict_items ([('S2','Lili'), (1,'a'), (2,'b'), ('S6','Musker'), ('S1','Jack')])#generate default dict through a list there's a pit that can't be explained .>>> ([Dict.fromkeys],'TESTD'){1:'TESTD', 2:'TESTD', 3:'TESTD'}

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Cyclic dict

# Method 1  for inch Info:     Print (Key,info[key]) # Method 2  for inch # will first turn the dict into a list, the data in the big time Mo    Print (K,V)

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A collection is an unordered, non-repeating combination of data, and its main functions are as follows:

• Go to the weight, turn a list into a set, and then automatically go heavy.
• Relationship test, test the intersection of two sets of data, difference set, and the relationship between the set

Common operations

s = set ([3,5,9,10])#create a collection of valuesT= Set ("Hello")#Create a collection of unique charactersa= T | S#the set of T and Sb= T & S#intersection of T and SC= T–s#differential Set (items in T, but not in s)D= T ^ s#symmetric difference sets (items in t or S, but not both)Basic operation: T.add ('x')#Add an itemS.update ([10,37,42])#adding multiple items in Suse Remove () to delete an item: T.remove ('H'Len (s) set length xinchs tests if X is a member of S X not inchs tests if X is not a member of S S.issubset (t) s<=T Test if every element in S is in T S.issuperset (t) s>=T Test if every element in T is in S s.union (t) s|T returns a new set containing each element in S and T S.intersection (t) s&T returns a new set containing the common elements in S and T S.difference (t) s-T returns a new set containing an element in s but not in T S.symmetric_difference (t) s^T returns a new set containing a non-repeating element in S and T S.copy () returns a shallow copy of the set "s"

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Python Dictionary and Collection operations