Python tutorial- string manipulation


String manipulation


A string can be treated as a tuple. However, Python provides some useful methods to manipulate strings.

lower() and upper() methods:


To make a string contain only lower case letters, you can use lower() method. In contrast, upper() method converts all letters of a string to upper case letters.


>>> st='Hello World'
>>> st.lower()
'hello world'
>>> st.upper()
'HELLO WORLD'
>>>

replace() and find() methods:


The replace() method will replace an old substring with a new substring. This method will not modify the string. It only returns a new string with the replacement.
>>> st.replace('World','Mr.Vibol')
'Hello Mr.Vibol'
>>> st
'Hello World'
>>> 
To find a substring in a string, you can use find() method. The find() method will return a index of the substring. If the substring is not in the string, it will return -1.
>>> st.find('or')
7
>>> st.find(',')
-1
 

startswith() and endswith() methods:


You test whether a string starts with or ends with a substring. These methods return True if the string starts with or ends with the substring, otherwise False.
>>> st.startswith('da')
False
>>> st.startswith('He')
True
>>> st.endswith('ol')
False
>>>  split() and join() methods:
The split() method will split a string by a separator.
>>> fullname=raw_input("Please enter your name separated by space:")
Please enter your name separated by space:Yuk Sovandara
>>> fname=fullname.split(' ')[0]
>>> fname
'Yuk'
>>> lname=fullname.split(' ')[1]
>>> lname
'Sovandara'
>>> 
To join substrings together to generate a string, you can use join() method:
>>> lst=['1','2','3','4','5']
>>> '+'.join(lst)
'1+2+3+4+5'
  Note: the first substring is treated as a separator in joining operation.




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