Python basic two--data type first knowledge

1, Integer int

int is primarily used to calculate-----"i.bit_length ()": Represents the minimum number of bits that I occupy.

#int-----i.bit_length (): Indicates the minimum number of bits that I occupy. I= 13print (I.bit_length ())

2, Boolean bool

There are two types of Boolean values: True,false. is the correct condition of the reaction.

True 1 true.

False 0 false.

3. String str

String is mainly used for storing a small amount of data, and subsequent operations.

integer int and string str convert to and from each other:

int---> str str (int)

STR----> int int (str) str can only be a combination of numbers at this time

Conversions between INT and bool BOOL:

int----> BOOL non 0 O'Clock value is True, 0 is False

BOOL----> int true converts to an integer int with a value of 1,false converted to an integer int type value of 0

# int---> bool      non 0 O'Clock value is true, 0 is Falsea = bool (2) b = bool (0) print (a)             #运行结果: Trueprint (b)             #运行结果: False#bool ---> int        True Converts the value of the int literal to 1,false to integer int with a value of 0c = Int (true) d = Int (False) print (c)             #运行结果: 1print (d)             # Run Result: 0　　

Mutual conversions between the string STR and the boolean bool:

STR---> BOOL non-null return value is true, NULL return value is False
BOOL---> str str (True) str (False)

#str--    the bool non-null return value is true, and the null return value is Falsei = bool (' 3 ') print (i)           #运行结果: Truei = bool (0) print (i)           #运行结果: Falsei = BOOL (") print (i)           #运行结果: False#bool--– Str str (TRUE) str (     False) i= str (true) print (i)           # Run Result: truei= str (FALSE) print (i)           #运行结果: False

Common Knowledge point Additions: If conditional statements and while loop statements are used for conditional judgments.

If 1:    print (' a ') Else:    print (' B ')       #运行结果: AIF 0:    print (' a ')      else:    print (' B ')       # Run Result: bwhile True:    print (' a ')    break            #运行结果: Awhile 1:             # and while True compare the execution efficiency of while 1 high   print (' B ')   break             #运行结果: b

4. Indexing and slicing of strings

　The index is subscript, that is, the elements of the string begin with the first, the initial index is 0, and so on.

A = "a1b2c3" Print (a[0])           #运行结果: Aprint (a[1])           #运行结果: 1print (a[2])           #运行结果: b

A slice is a section of a string that is truncated by an index (START index: Stop index: Step), forming a new string (the principle is that Gu head ignores butt).

A = ' Abcdefghijk '
Print (A[0:3])                    
Print (A[2:5])
Print (a[0:])  #默认到最后
Print (a[:])  #从头到尾
Print (A[0:-1]) #-1 is the last one.
Print (A[0:5:2]) #加步长
Print (A[5:0:-2]) #反向加步长
Print (A[-1:-6:-2]) #反向取加步长

The output of the above code:

Abccdeabcdefghijkabcdefghijkabcdefghijacefdbkig

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String Common methods: format is similar to formatted output but each has a different application scenario.

#第一种s = ' I'm {}, this year {}, height {} '. Format (' Jinxin ', 21,175) print (s) #第二种s = ' I'm {0}, this year {1}, height {2}, I still call {0} '. Format (' Jinxin ', 21,175) Print (s) #第三种s = ' I'm {name}, this year {age}, height {high} '. Format (name = ' Jinxin ', high=175,age=21) print (s)　

Common methods of strings

s="aBc D12%h&j ("Print(S.capitalize ())#capitalize the first letter of the string run result: ABC d12%h&j (Print(S.swapcase ())#Case Rollover Run Result: AbC d12%h&j (Print(S.title ())#non-letter-separated place first uppercase, other lowercase run result: ABC d12%h&j (Print(S.upper ())#ALL caps Run Result: ABC d12%h&j (Print(S.lower ())#large all lowercase run result: ABC D12%h&j (Print(S.center (25))#Center content Run Result: ABc d12%h&j (Print(S.center (25,'*'))#Center content on both sides with * fills the running result: *******ABC d12%h&j (******Print(S.expandtabs ())#the tab symbol (' \ t ') in the string is converted to a space, and the tab symbol (' \ t ') default number of spaces is 8Print(S.find ('D'))#through the element to find the index, can look for the whole, can slice, can't find return-1 run Result: 4Print(S.index ('D'))#through the element to find the index, you can look for the whole, can be sliced, can't find the error running result: 4Print(S.startswith ('a'))#checks whether the string starts with the specified substring, or returns True if it is, otherwise FalsePrint(S.endswith ('('))#checks whether the string ends with the specified substring, returns True if yes, otherwise returns FalsePrint(S.strip ())#Remove the space at the front and back of the string, line breaks, tab keys, or specified characters. Run Results: ABc d12%h&j (Print(S.lstrip ())#truncate the left space of a string or specify a character to run the result: ABc d12%h&j (Print(S.rstrip ())#truncate the space to the right of the string or specify the character to run the result: ABc d12%h&j (Print(S.split ('b', 3))#slices A string by specifying a delimiter--->list run result: [' aBc d12%h&j (')Print(S.replace ('a','Small', 2))#replace the "a" in the string with "small" 2 run results: small BC D12%H&J (Print(S.isalnum ())#A string consists of a letter or a number running the result: FalsePrint(S.isalpha ())#The string consists only of letters. Run Result: FalsePrint(S.isdigit ())#string only consists of numbers run result: FalsePrint(S.count ('a'))#counts the number of occurrences of "a" in a string. Run Result: 1Print(Len (s))#calculates the length of the string "s" or the number of items running results:#Strip application Examples:Name = input ('Please enter your first name:'). Strip ()ifName = ='Alex':    Print('Somebody')Else:    Print('Please re-enter')#Upper and lower application examples, all uppercase and all lowercase actual application: Case-insensitive verification code. Code ='Aedd'Your_code= Input ('Please enter the verification code:')ifYour_code.upper () = =code.upper ():Print('Enter the correct')Else:    Print('Please re-enter')

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Python basic two--data type first knowledge