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How do I turn a list into a string in Python?

Python 2 min read Full lesson: Python Basics — Lists, Dictionaries and Functions
Short answer

Use separator.join(items). The separator is the string you call the method on, and every item must already be a string.

python
tracks = ["Python", "PHP", "Ruby"]

", ".join(tracks)      # 'Python, PHP, Ruby'
"".join(tracks)        # 'PythonPHPRuby'
"\n".join(tracks)      # each on its own line

The syntax looks backwards until you notice why: the separator is what does the joining, and it works with any iterable, not just lists.

#The error everyone hits first

python
", ".join([1, 2, 3])
# TypeError: sequence item 0: expected str instance, int found

join will not convert for you. Map first:

python
", ".join(str(n) for n in [1, 2, 3])     # '1, 2, 3'
", ".join(map(str, [1, 2, 3]))           # same thing

#Why not just concatenate in a loop?

python
result = ""
for item in tracks:
    result += item + ", "        # slow, and leaves a trailing comma

Strings are immutable, so every += builds a whole new string. On a big list that is quadratic work. join allocates once.

#Going the other way

python
"Python, PHP, Ruby".split(", ")     # ['Python', 'PHP', 'Ruby']
"a b  c".split()                    # ['a', 'b', 'c'] — any whitespace, no empties
"a,b,c".split(",", 1)               # ['a', 'b,c'] — split at most once

Note that bare .split() with no argument collapses runs of whitespace and drops empty strings, which is usually what you want for prose.

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