NLTK——常用函数
1.Functions Defined for NLTK's Frequency Distributions
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| Example | Description |
|---|---|
| fdist = FreqDist(samples) | create a frequency distribution containing the given samples |
| fdist[sample] += 1 | increment the count for this sample |
| fdist['monstrous'] | count of the number of times a given sample occurred |
| fdist.freq('monstrous') | frequency of a given sample |
| fdist.N() | total number of samples |
| fdist.most_common(n) | the n most common samples and their frequencies |
| for sample in fdist: | iterate over the samples |
| fdist.max() | sample with the greatest count |
| fdist.tabulate() | tabulate the frequency distribution |
| fdist.plot() | graphical plot of the frequency distribution |
| fdist.plot(cumulative=True) | cumulative plot of the frequency distribution |
| fdist1 |= fdist2 | update fdist1 with counts from fdist2 |
| fdist1 < fdist2 | test if samples in fdist1 occur less frequently than in fdist2 |
2.Some Word Comparison Operators
| Function | Meaning |
|---|---|
| s.startswith(t) | test if s starts with t |
| s.endswith(t) | test if s ends with t |
| t in s | test if t is a substring of s |
| s.islower() | test if s contains cased characters and all are lowercase |
| s.isupper() | test if s contains cased characters and all are uppercase |
| s.isalpha() | test if s is non-empty and all characters in s are alphabetic |
| s.isalnum() | test if s is non-empty and all characters in s are alphanumeric |
| s.isdigit() | test if s is non-empty and all characters in s are digits |
| s.istitle() | test if s contains cased characters and is titlecased (i.e. all words in s have initial capitals) |
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