The join() and split() functions in Python are both important methods for processing strings, but their functions are exactly the opposite.
join() function:Concatenate string elements in iterable objects (such as lists, tuples) into a string.
split() function:Split the string into multiple substrings by the specified delimiter, returning a list of these substrings.
1. Functional differences
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split()effect: Used to split a string according to the specified delimiter and return a list of strings.
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grammar：
(sep=None, maxsplit=-1)。-
sep: The specified delimiter, default is a space (including any white space, such as spaces, line breaks\n, tab characters\twait). If there is a blank character at the beginning or end of a string, the default will also be ignored. -
maxsplit: How many times can be performed at most, the default is-1, means unlimited segmentation.
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example：
mystr = "apple,banana,cherry"
result = (",") # Use commas as separatorprint(result) # Output: ['apple', 'banana', 'cherry']mystr2 = "apple banana\tcherry\norange"
result2 = () # By default, split by whitespaceprint(result2) # Output: ['apple', 'banana', 'cherry', 'orange']-
join()effect: Used to concatenate string elements in an iterable object (such as lists, tuples, etc.) to form a new string.
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grammar：
(iterable)。-
str: A string used for concatenation, that is, a string as a separator. -
iterable: Iterable object containing string elements. If it is not a string, it will be thrownTypeError。
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example：
mylist = ["apple", "banana", "cherry"] result = ",".join(mylist) # Use commas as a linkerprint(result) # Output: apple,banana,cherry
2. Differences in usage scenarios
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split()-
Data analysis: When you obtain string data from text files, network data, etc., and need to split it into multiple parts for processing,
split()Very useful. For example, parse CSV format data, log files, etc. -
String formatting: When processing strings entered by users or string data obtained from other systems, you can use them
split()Perform formatting to extract the required information.
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Data analysis: When you obtain string data from text files, network data, etc., and need to split it into multiple parts for processing,
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join()-
String stitching: When you need to combine multiple string elements into a complete string, use
join()Compared to use+More efficient. Especially when dealing with large amounts of string splicing,join()The performance advantages are obvious. -
Generate report or output format: When generating text reports, JSON format data, HTML content, etc., you need to combine data elements into strings that meet a specific format,
join()It's a great choice.
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String stitching: When you need to combine multiple string elements into a complete string, use
3. Differences in input and output types
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split()-
enter: The caller is a string,
split()The parameters of the method can be strings (delimiters), numbers (maxsplit)wait. - Output: Returns a list of strings.
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enter: The caller is a string,
numbers = [1, 2, 3]
# print(",".join(numbers)) # ❌ An error will be reported: TypeError: sequence item 0: expected str instance, int found#Solution: Convert numbers to strings firstnumbers = [1, 2, 3]
result = ",".join(map(str, numbers))
print(result) # "1,2,3"-
join()- enter: The caller is a string (connector), and the parameter is an iterable object (such as lists, tuples).
- Output: Returns a new string.
IV. Reversibility
Generally speaking, in some casessplit()andjoin()The operations can "counter" each other (under appropriate conditions). For example, if you use a specific separator to do a stringsplit(), then use the same separator andjoin()Combine the result list and you can get the original string (if there are no other exceptions such as empty strings, etc.). This reflects their complementarity in certain operations.
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