the string data type python--

String: quoted by the wrap

Null character: there is no character
blank character: there are content, content is the spacebar

python is any data can be converted to a Boolean value

print (bool (s1)) # s1 no content data, is converted to a boolean value False
Print (BOOL (s2)) # s2 in the content data, is converted to a Boolean True

Numeric type into a string

STR = S3 (num_5)
Print (type (S3), S3)
- by str () function, the value type can be converted to a string

String Manipulation

1. --- index value can be positive sequence values, the values may be reverse; positive sequence index value starting from 0, descending the index value starting from -1;
   EG: STR = 'Hello Python' n ----- sequence index: res1 = str [0]; inverted index: res2 = str [-1]

2. --- slice taken out of the string value or - String
   2.1 str [m: n] --- m is the start index, n + 1 is the ending index, taking the end of the head does not take
   2.2 str [: n] - - writing start position is not the default scratch
   2.3 str [m:] --- not write end position, the default end
   
   2.4 str [m: n: k ] --- is step by step sections, k, is take a number
   

3. String concatenation
   3.1 + Number splicing EG: STR = str2 str1 +
   3.2 The method of the Join string x.join ((string1, string2 2)) eg:. Str3 = ',' join ((str, str1)), join which is a parameter, so the composition of a string to be connected into the tuple list or

4. String escape
   \ n: newline \ t: tab r: content can force the output of all strings, without escaping
   

Based approach of the string

1. Find elements
   str.find ( "a", m) ---- a is an element you want to find, the value of m is an element m from the index to start looking; m not write anything, the index value from 0 position to start looking
   

2. (), The number of statistical elements appear in the string count
   

3. replace (), the replacement string element
   

4. Split (), cutting strings, after cutting returns a list of types of data
   

5. String case conversion, upper () / lower ()
   

Formatted output string

1. formatted output format
2. Traditional conventional format output format output ----%% s% d% f
3. F expression (the new version is available, expand knowledge)
   
   

decimal format specified output: {:. 2f} - Specifies the output 2 decimals