Checking whether a string starts with XXXX

Question

I would like to know how to check whether a string starts with  hello  in Python   In Bash I usually do   if      string      hello     then  do something here fi   How do I achieve the same in Python

User · Answer

RanRag has already answered it for your specific question.

However, more generally, what you are doing with

if [[ "$string" =~ ^hello ]]

is a regex match. To do the same in Python, you would do:

import re
if re.match(r'^hello', somestring):
    # do stuff

Obviously, in this case, somestring.startswith('hello') is better.

User · Answer

In case you want to match multiple words to your magic word  you can pass the words to match as a tuple    gt  gt  gt  magicWord    zzzTest   gt  gt  gt  magicWord startswith   zzz    yyy    rrr    True   startswith takes a string or a tuple of strings

User · Answer

I did a little experiment to see which of these methods  string startswith  hello   string rfind  hello      0 string rpartition  hello   0        string rindex  hello      0  are most efficient to return whether a certain string begins with another string  Here is the result of one of the many test runs I ve made  where each list is ordered to show the least time it took  in seconds  to parse 5 million of each of the above expressions during each iteration of the while loop I used    startswith  1 37    rpartition  1 38    rfind  1 62    rindex  1 62     startswith  1 28    rpartition  1 44    rindex  1 67    rfind  1 68     startswith  1 29    rpartition  1 42    rindex  1 63    rfind  1 64     startswith  1 28    rpartition  1 43    rindex  1 61    rfind  1 62     rpartition  1 48    startswith  1 48    rfind  1 62    rindex  1 67     startswith  1 34    rpartition  1 43    rfind  1 64    rindex  1 64     startswith  1 36    rpartition  1 44    rindex  1 61    rfind  1 63     startswith  1 29    rpartition  1 37    rindex  1 64    rfind  1 67     startswith  1 34    rpartition  1 44    rfind  1 66    rindex  1 68     startswith  1 44    rpartition  1 41    rindex  1 61    rfind  2 24     startswith  1 34    rpartition  1 45    rindex  1 62    rfind  1 67     startswith  1 34    rpartition  1 38    rindex  1 67    rfind  1 74     rpartition  1 37    startswith  1 38    rfind  1 61    rindex  1 64     startswith  1 32    rpartition  1 39    rfind  1 64    rindex  1 61     rpartition  1 35    startswith  1 36    rfind  1 63    rindex  1 67     startswith  1 29    rpartition  1 36    rfind  1 65    rindex  1 84     startswith  1 41    rpartition  1 44    rfind  1 63    rindex  1 71     startswith  1 34    rpartition  1 46    rindex  1 66    rfind  1 74     startswith  1 32    rpartition  1 46    rfind  1 64    rindex  1 74     startswith  1 38    rpartition  1 48    rfind  1 68    rindex  1 68     startswith  1 35    rpartition  1 42    rfind  1 63    rindex  1 68     startswith  1 32    rpartition  1 46    rfind  1 65    rindex  1 75     startswith  1 37    rpartition  1 46    rfind  1 74    rindex  1 75     startswith  1 31    rpartition  1 48    rfind  1 67    rindex  1 74     startswith  1 44    rpartition  1 46    rindex  1 69    rfind  1 74     startswith  1 44    rpartition  1 42    rfind  1 65    rindex  1 65     startswith  1 36    rpartition  1 44    rfind  1 64    rindex  1 74     startswith  1 34    rpartition  1 46    rfind  1 61    rindex  1 74     startswith  1 35    rpartition  1 56    rfind  1 68    rindex  1 69     startswith  1 32    rpartition  1 48    rindex  1 64    rfind  1 65     startswith  1 28    rpartition  1 43    rfind  1 59    rindex  1 66    I believe that it is pretty obvious from the start that the startswith method would come out the most efficient  as returning whether a string begins with the specified string is its main purpose  What surprises me is that the seemingly impractical string rpartition  hello   0        method always finds a way to be listed first  before the string startswith  hello   method  every now and then  The results show that using str partition to determine if a string starts with another string is more efficient then using both rfind and rindex  Another thing I ve noticed is that string rindex  hello      0 and string rindex  hello      0 have a good battle going on  each rising from fourth to third place  and dropping from third to fourth place  which makes sense  as their main purposes are the same  Here is the code  from time import perf counter  string    hello world  places   dict    while True      start   perf counter       for   in range 5000000           string startswith  hello       end   perf counter       places  startswith     round end - start  2       start   perf counter       for   in range 5000000           string rfind  hello      0     end   perf counter       places  rfind     round end - start  2       start   perf counter       for   in range 5000000           string rpartition  hello   0            end   perf counter       places  rpartition     round end - start  2       start   perf counter       for   in range 5000000           string rindex  hello      0     end   perf counter       places  rindex     round end - start  2           print  f  b    str a  ljust 4   quot 4 quot     for a  b in sorted i   -1  for i in places items

User · Answer

Can also be done this way    regex re compile   hello       THIS WAY YOU CAN CHECK FOR MULTIPLE STRINGS    LIKE    regex re compile   hello  john  world    if re match regex  somestring       print  Yes

User · Answer

aString    hello world  aString startswith  hello     More info about startswith

[python] Checking whether a string starts with XXXX

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