Three methods of Python string connection and their efficiency and application scenarios

The Python string connection method, generally has the following three kinds:

Method 1: Connect directly via the plus (+) operator

Website = ' python ' + ' tab ' + '. com '

Method 2:join Method

Liststr = [' Python ', ' tab ', '. com '] website = '. Join (LISTSTR)

Method 3: Replace

Website = '%s%s%s '% (' python ', ' tab ', '. com ')

Let's take a look at the difference between the three ways.

Method 1, simple and straightforward to use, but many online people say this method is inefficient

The reason why Python uses + for string connections is inefficient because the strings in Python are immutable types, a new string is generated when using + to concatenate two strings, and a new string is required to re-request the memory, when the string of successive additions is many (a+b+c+d+ e+f+ ...) , inefficiency is inevitable.

Method 2 uses a slightly more complex, but high-efficiency connection to multiple characters, with only one memory request. And if the character of the list is connected, this method must be the preferred

Method 3: String formatting, this method is very common, I also recommend the use of this method

The following experiment is used to illustrate the efficiency of string connections.

Compare objects: Plus connection VS join connection Python version: python2.7 system environment: CentOS

Experiment One:

#-*-Coding:utf-8-*-from time import timedef method1 (): T = time () for I in Xrange (100000): s = ' Pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' Pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' + ' pythontab ' + ' Pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' Pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + '    Pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab ' Print time ()-TdeF method2 (): T = time () for I in Xrange (100000): s = ". Join ([' Pythontab ', ' pythontab ', ' Pyth Ontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' Pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' Pythontab ',' Pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' Pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' Pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' pythontab ', ' Pythontab ']) print time ()- Tmethod1 () method2 ()

Results:

0.6416959762570.341440916061

Experiment Two:

#-*-Coding:utf-8-*-from time import timedef method1 ():    t = time () for    I in Xrange (100000):        s = ' pythontab ' + ' pythontab ' + ' pythontab ' + ' pythontab '    print Time ()-TdeF method2 ():    t = time () for    I in Xrange (100000):        s = '. Join ([' Pythontab ', ' pythontab ', ' pythontab ', ' Pythontab '])    print time ()-tmethod1 () method2 ()

Results:

0.02656912803650.0522091388702

The above two experiments have completely different results, the only difference between the two experiments is: the number of string connections.

Conclusion: The low-plus connection is inefficient when multiple strings are connected consecutively, and if the number of connections is less, the plus connection efficiency is higher than the join connection efficiency.

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