Python 6 basic functions of numeric and Boolean values and strings

Data type: View variable data types type (variable) or print (type (variable))

integer int : A natural number without decimals, also called an integral type. In the 2. The x version is also divided into long integers and shaping. But in 3. Unity in the X version is called an integer or integral type.

Create: A = 123 or a = Int (123) The result is the same as the integer a = "123" is the string

Conversion: new_a = Int (a) conversion can only be converted. For example, if A is ABC, then this cannot be converted to int type.

boolean bool : used primarily for condition determination after the if elif while.

True: You can assign a value to a variable such as a = True

False: You can assign it to a variable such as a = False

conversion:BOOL (variable or number) is only 0 or empty, the result is false when converted to a bool value.

a few special conversions:

Name = ""

name1 = "Space"

A = bool ("space") converts a space directly to bool to get false.

A = bool (NAME1) Converts the variable to a space, and the bool will get true.

A = bool (name) variable the value of name does not exist, at which time the conversion result is false

string str :

Created: a = "123", a = ' 123 ', a = str (123) A = str (123)

Conversion: b = 123 A = str (b)

string concatenation: a = "Hello" b = "World" A + b = ' HelloWorld '

string formatting:%+[s.d , etc.]. % is called a placeholder:

①a = "This is%s year,%s month%s Day"% (2017,4,29) The final result is a = "This is 2017, April 29."

The ② percent is called a placeholder, the red% is the delimiter, and the subsequent 2017 4 29 will correspond to the placeholder in the replacement quotation mark if there is only one

The number of values to be mapped in there is no parentheses behind.

The s that follow the ③ percent sign are formatted as strings for the characters that are mapped to%, and d for formatting as numbers.

You can also write as follows:

A = "This is%s year,%s month%s Day"

New_a = A% (2017,4,29)

Result New_a = "This is 2017, April 29"

string manipulation:

Remove or replace left and right spaces and \ n newline characters:

For example: A = "ABC" a_new = A.strip (value x).

Srtip replace both spaces with the value x Lstrip replace the left space as the value x Rstrip replace the right space with the value x. The value can be empty.

Value: Can be filled with nothing this is tantamount to removing both sides of the space, if filled with that is to replace both sides of the space.

Example 1:a = "abc" a_new = A.strip () The result is a_new = "abc" Remove space

Example 2:a = "ABC" a_new = A.strip (@) result is a_new = "@[email protected]" replace both ends with a space of @

Example 3: A = "ABC" a_new = A.lstrip (@) result is a_new = "@ABC" replaces the left space is @

Example 4:a = "ABC" a_new = A.rstrip (@) result is a_new = "[email protected]" Replace right space @

Split: variable name. Split (' split boundary identifier ') split or rsplit from right to left.

Example: Name = "Admin*armin*guest"

Example 1 new_name = Name.split (' * ') where. is the dividing line, the result is new_name = [' admin ', ' Armin ', ' guest ']

Example 2 new_name = Name.split (' * ', 2) meaning left to right is divided into the 2nd * symbol. [' admin ', ' Armin ', ' guest ']

Numbers with negative values are the same as the numbers that are not written.

Example 3 new_name = Name.rsplit (' * ', 2) meaning right to left has been divided into the 2nd * symbol [' admin ', ' Armin ', ' guest ']

Length: The length in Python3 is calculated according to the number of characters. Python2 Chinese is calculated by 2 characters.

name = ' Armin ' V = len (name) print (V) can see a length of 5. Interactive mode len (variable name) to see the length.

Index: Used to remove a specific value

Name = "Armin" V = name[1] Print (v) is R. The code means that the value of position 1 is taken out of the Armin,

The position is counted from 01234, and 0 represents the first bit.

Loop out the values in turn:

'Armin'i = 0 whilei < 5: v =print(v) i + = 1       

Slices: As with the index function, it is to get out the value. The difference is that the slice takes a character, so only one character can be taken.

The rule of value: The ① packet before the packet is 0:4 actually only 1234 locations. [Start: End: Step x] Start with

The end must be on the left side of the end compared to the position.

② step span is X-1, that is, if you enter 2, then take the first one after the middle one and then take down one

Analogy. 0::2 means to take the value of step 2 from beginning to end.

Left to right position ordinal 0 1 2 3 4

String a r m i n

Right-to-left position sequence number-5-4-3-2-1

"Armin" name = Name[0:4] means to  take 1-3 bits of name and assign to nameprint'Armin'print (name[ 0:2]) Prints the 1-2 bits in name. 

Python 6 basic functions of numeric and Boolean values and strings