Built-in functions learned by the python tribe, python tribe

Built-in functions learned by the python tribe, python tribe

Recently, I joined the python tribe. I felt that it was very interesting. I had a bit of fun. I learned a lot of built-in functions that I didn't know before, and I felt that I was about to remember them. So I started to display them.

1. divmod (a, B): Take the quotient and remainder of a divided by B, and the effect is equivalent to (a/B, a % B );

2. dir (): the parameter is the function name and class name. It tells us what parameters are contained in the corresponding function.

3. enumerate: The serial number is generated when the list is traversed. For example:

1 a = [1, 2, 3]2 for index,item in enumerate(a):3     print index4     print item

4. complex: process the plural values in python, such as complex (2, 3) --> 2 + 3j; complex (2 + 3j) --> 2 + 3j note that the expressions in the brackets cannot contain spaces !!

5. cmp (x, y): The function is used to compare two objects. If x <y returns-1, if x = y, 0 is returned. If x> y, 1 is returned.

6. chr (I): returns the ASCII character corresponding to the integer I. Opposite to ord.

7. isinstance (a, obj): used to determine the type of an object, which indicates whether a is of the obj type. Here, pay attention to the type function. One of the most important differences between them is: type can only be used to directly determine the type, while isinstance is more powerful than type, and can be used to subclass

8. Differences between any and all: any and all () functions. any is arbitrary, and all is all. Any ----> if no iterable element is 0, '', False, all (iterable), True is returned. If iterable is null, False is returned. Functions are equivalent:

def any(iterable):     for element in iterable:        if  element:            return False    return True

 

 

 

However, if all the elements of iterable are not 0, '', False, or iterable is null, all (iterable) returns True; otherwise, False is returned. The function is equivalent:

1 def all(iterable):2     for element in iterable:3         if not element:4             return False5     return True

9. _ doc __: python function Description document string, print (function. _ doc _), which outputs the description enclosed by three quotation marks in the function.

10. eval: Evaluate the string 'str' as a valid expression and return the calculation result. You can also execute string code.

11: exec, execfile,execThe statement is used to execute the Python statement stored in a string or file. The execfile (filename [, globals [, locals]) function can be used to execute a file.

12: format -----> python built-in Formatting Function. usage found on the Internet:

 

1 age = 25 2 name = 'caroline '3 def test: 4 print '{0} is {1} years old. '. format (name, age) # output parameter 5 print '{0} is a girl. '. format (name) 6 print '{0 :. 3} is a decimal. '. format (1/3) # three digits after the decimal point 7 print '{0: _ ^ 11} is a 11 length. '. format (name) # Use _ to fill the blank space 8 # Replace the alias with 9 print '{first} is as {second }. '. format (first = name, second = 'wendy ') 10 print 'My name is 255.0.name+'.format(open('out.txt', 'w') # Call method 11 print 'My name is }. '. format ('fred ') # specify the width

 

 

 

I learned this first, and I have to go to work again ....

----- Python pupils